My sister, whom I raised, has turned evil after faking her death for three years.

At 10 a.m. the next day, the educational materials section on the second floor of Xinhua Bookstore was so quiet that only the hum of the air conditioner could be heard.

Jiang Ran sat at a long table by the window, a sketchbook open in front of her, a colored pencil in her hand, intently sketching and drawing.

She looked very serious, her little head slightly lowered, her two little legs swinging back and forth under the chair.

But if someone went around to look at her from behind, they would find that her eyes were not fixed on the drawing paper at all, but were glancing to the side every now and then.

Three meters away, Su Qing was standing in front of the elementary school textbook shelf, flipping through a book called "Third Grade Mathematical Thinking Training" in her hand, her brows furrowed so deeply they could trap a mosquito.

Jiang Ran quickly looked away, her pen flying across the notebook.

A figure gradually emerged on the drawing paper, with long hair, slightly furrowed brows, and clean, crisp lines in profile.

She drew the older sister, and even drew the detail that when Su Qing frowned, her left eyebrow would be slightly higher than her right eyebrow.

Jiang Ran pursed her lips and smiled secretly, then quickly lowered her head, pretending that she had been drawing seriously.

Su Qing was completely unaware of this.

When she turned to the fourth page of the book and saw the phrase "chicken and rabbit in the same cage," her temples began to throb.

Turning to the fifth page, the words "cows eating grass problem" felt like a slap in the face.

Turning to page six, in the "Meeting Problem," two trains depart from points A and B, heading towards each other. She felt that she also wanted to depart from this book, heading towards each other.

[System notification: Slight fluctuations detected in host's heart rate and blood pressure. Host is advised to take deep breaths and maintain emotional stability.]

Su Qing closed the book expressionlessly and then picked up another book, "Complete Guide to Basic Elementary School Mathematics Knowledge".

Turn to the first page, the four arithmetic operations. Not bad.

Turning to the second page, fractions and decimals. Barely tolerable.

She turned to the third page, the beginner's equations. She stared at the "x" for five seconds, a genuine question surfacing in her mind: why does a letter represent an unknown number? If you don't know it, why calculate it?

She slammed the book shut, leaned against the bookshelf, and looked up at the ceiling.

"system."

[Yes, host.]

  

I have a question for you.

[Please speak.]

"Can you just cram all the elementary school math knowledge into my brain? Like in the movies, a flash of light, and I know it all."

The system was silent for two seconds.

[Assessing host requirements... Assessment complete.]

[I'm sorry, host.]

[The core function of this system is to monitor your health indicators and provide health management advice; it does not have knowledge transfer capabilities.]

[According to the system's database, similar functions typically appear in science fiction works, and their scientific basis and technical methods have not been verified.]

[It is recommended that the host acquire elementary school math knowledge through conventional learning methods. This is of great importance for you to fulfill your responsibilities as a guardian and tutor Jiang Ran.]

Learning is a gradual process. Please adopt a proper learning attitude and become a cultured guardian.

Su Qing's lips twitched after hearing this earnest analysis.

"Wasn't the last sentence of what you just said the key point?"

[The host has a very strong comprehension ability.]

"hehe……"

Su Qing silently reopened the book, staring at the numbers and symbols, and let out a heartfelt sigh from the depths of her soul: "I don't understand."

[What doesn't the host understand?]

"Why would anyone invent mathematics? Tell me, in ancient times, humans were just hunting, gathering fruit, sleeping in caves, living perfectly well. Who was the idiot who came up with the idea of ​​doing math?"

[The question posed by the host touches upon the history of mathematics. As a fundamental discipline, mathematics can be traced back to early human beings' need to understand quantity, space, and time...]

"Stop," Su Qing interrupted expressionlessly, "I wasn't really asking you."

[…Good host.]

Su Qing flipped through the basic knowledge book in her hand again. When she saw the page on "Area Formula", her eyes went from confusion to bewilderment, from bewilderment to emptiness, and finally fixed on a dangerous glint that seemed to want to stuff the book into a shredder.

She muttered under her breath, speechless: "The area of ​​a rectangle is equal to its length multiplied by its width, and the area of ​​a triangle is equal to its base multiplied by its height divided by two."

"So why should a triangle be divided by two? Just because it has one less side than a rectangle, does that mean it deserves to be cut in half?"

The system wisely refrained from responding.

Just as Su Qing was about to put the fifth supplementary textbook of the day back on the bookshelf, a voice came from the side.

"This book is really poorly written."

Su Qing turned her head and saw a young woman standing next to her, also holding a primary school math textbook, looking at her with the kind of look one might give a fellow human.

The woman looked to be in her early twenties, with well-maintained skin. She wore a light blue dress and her hair was loosely tied in a low ponytail at the back of her head. She looked neat and tidy, and when she smiled, there were fine laugh lines at the corners of her eyes, which made her seem even more approachable.

Su Qing made the above observations and analyses on the physical characteristics of young women.

But what Su Qing didn't know was that the "young woman in her twenties" standing in front of her was Sun Yaqin, the biological mother of Cheng Xiaoyu and Cheng Xuyan.

Sun Yaqin came to the bookstore today for a simple reason: to buy two workbooks for her youngest son.

Cheng Xiaoyu, that chubby kid, is okay at Chinese, but math is like an insurmountable wall for him.

She originally planned to just grab two books at the cashier and leave, but when she passed by the elementary school supplementary materials section, she happened to hear a young woman talking to herself.

"The area of ​​a rectangle is equal to its length multiplied by its width, the area of ​​a triangle is equal to its base multiplied by its height divided by two... Why should the area of ​​a triangle be divided by two?"

These words were so sincere and heartfelt that Sun Yaqin immediately felt a strong resonance with them.

She recalled learning the area formula when she was a child, and drawing a triangle on a piece of scrap paper, then staring at it blankly for a long time.

Why doesn't a triangle deserve a complete base times height? This question puzzled her for an entire semester.

So she stopped and glanced at the book in the girl's hand—"The Complete Guide to Basic Elementary Mathematics Knowledge"—and then at the expression on the girl's face—that tragic feeling of being hurt by mathematics and having no choice but to continue being hurt by it was all too familiar.

Sun Yaqin decided to strike up a conversation.

"This book is really poorly written," she said, pointing to the comprehensive book in Su Qing's hand. "There are too few examples, and the explanations aren't clear enough. Many kids still have to rely on their parents to explain things to them after buying it. If you're looking for supplementary materials, the blue one next to you is much better."

Su Qing looked in the direction she was pointing and found it was a book called "Elementary School Mathematics Mind Maps". The cartoon numbers on the cover were giving her a friendly smile.

"Thank you," Su Qing picked up the blue-covered book and flipped through it. She found that the example problems inside were indeed explained in more detail, and there were more illustrations, so it didn't seem so discouraging.

Su Qing breathed a sigh of relief and turned to the woman next to her, saying, "Are you also here to buy elementary school supplementary materials?"

Sun Yaqin smiled and replied naturally, "Yes, I'll buy them for my brother. He's not very good at math, and school starts soon, so I'll buy him two to practice."

Sun Yaqin was referring to "my brother".

She said those three words without batting an eye, her tone as natural as if she were describing what she had for breakfast that morning.

Su Qing was completely unaware, and Jiang Ran, engrossed in her drawing, paid no attention either. The only person present who should theoretically have noticed—the system—remained quietly in her consciousness, without making any move.

Sun Yaqin was secretly delighted.

She was very satisfied with her makeup and outfit today. She changed into two different outfits before leaving the house, and now it seemed to work well. The way this girl looked at her was clearly the way she would look at someone her own age.

She needs to tell Chengxu Yan when she gets back that her mother isn't old yet. (♡＞w＜)