In another world, Lu Mingfei is learning card making.

When the two returned to the lounge, the brown-haired girl was already waiting there.

After returning to Earth that Sunday, Lu Mingfei had even fewer memories of his already limited number of classmates, but thankfully there was still Rong En—

If you disregard his martial arts skills, which were "forced" out of him by his elders, he's just an ordinary student who enjoys dueling and card games, idolizing top card players like sports stars.

Therefore, he was actually quite familiar with the students around him.

"That person is indeed a freshman at the Knights' Academy, named... Lacey Kinster." On the way, Ron said thoughtfully, "She, well, doesn't really talk to other people often. She usually just stays in the library when she has nothing to do. We all say she's more like a Bachelor's Academy freshman than a Knights' Academy freshman—"

"If her card is the Knight of Study, she would definitely choose the Bachelor's College without hesitation—that's what we all say."

"Looking back now, she must have genuinely loved reading... so why wasn't she assigned to a bachelor's degree program?"

"Oh, her Sorting Card summoned a beaver, you know, the furry kind that gnaws on trees."

—Looking at her now, she really does look like a beaver.

Looking at her front teeth, Lu Mingfei couldn't help but sigh.

"So, um... you really want to learn arithmetic?" Lu Mingfei had her and Ron sat on a sofa, while he sat opposite them. Lace seemed to still be thinking about how Ron had used his wand to lift her to the ground earlier, so she deliberately kept some distance from him.

"If you'd like, I have two points to make. First, I'm not a professional teacher, so there might be some problems during my teaching. I also don't prepare lessons, so I can only speak as thoughts come to mind..."

Ron and Lace both nodded, indicating their acceptance. Lu Mingfei then proceeded to the second point:

"Secondly, I don't have the time to teach each of you individually. So from now on, after the first class in the afternoon, if you don't have any other classes, we'll still have a group lesson here. If you miss a class, I won't go over the material again."

"If that's acceptable... shall we start by learning the simplified symbolic representation of numbers?"

Every time this topic comes up, Lu Mingfei feels somewhat "exhausted".

There are no Arabic numerals in this other world, so each problem in that mental arithmetic workbook is represented by a long string of characters. As for the magical spirits' numerical representation? That's the result of an automatic translation from the internet; to everyone else in this world, it looks like three long strings of characters.

Lu Mingfei only had about half an hour to actually solve the problems; the remaining hour was spent translating the text problems into Arabic numerals and then translating the results back into text...

As a result, not only did I waste a whole class period of time, but now I have to go through the whole process with two other people?

Whenever Lu Mingfei thought about this fact, he felt that he might as well go back to Earth and be a student, at least then he wouldn't be tormented.

However, when it came to actually teaching her, Lais gave Lu Mingfei a pleasant surprise: she mastered Arabic numerals very quickly. Lu Mingfei only taught her for about ten minutes before she had grasped the correct way to represent them.

"How did you do that?" Lu Mingfei scratched his head and asked.

"Well, how should I put it? Although I've never seen this set of symbols before, I have seen this idea of ​​'using symbols to represent numbers' before," Lace replied, tidying her messy hair.

After Ron expressed his doubts, Raise recounted her life at home: she was the child of a minor nobleman living in the royal city, her father made a living by teaching children of higher-ranking nobles, and her mother had the privilege of studying under a sage.

It was only through her family's influence that she developed a love for reading, to the point that she spent her first week at school immersed in the library.

She had seen this line of thinking at the Auditors' Association in the royal city.

Auditors are professionals who specialize in providing tax services to banks and large business owners. They review these individuals' annual income and expenses and examine the economic laws enacted by the kingdom to ensure that these individuals pay reasonable taxes without being audited by the tax authorities and thus incurring fines.

To achieve this, one must have the ability to quickly calculate numbers and express them concisely.

"But the Auditors' Association takes their own 'rapid calculation' techniques extremely seriously; they don't even allow the meaning of the symbols they use to be leaked." Lacey stared intently at the Arabic numerals. "And you, Lu, your system is completely different from theirs..."

"It's best not to get caught by the Auditors Association..." Lais advised, but then suddenly remembered that the person in front of her was not an ordinary person without any background.

Lu Mingfei is the son of a hero. Even though he is usually carefree and unpretentious, he can easily transform this reputation into enormous political capital if he so chooses.

After all, the previous generation of heroes were reduced to ashes after slaying the Demon King, so people always have confidence and tolerance for the descendants of meritorious figures.

Lu Mingfei didn't notice the strange expression on Lai Si's face. He was just a little surprised—it turned out that the people from other worlds weren't stupid. It was just that someone had monopolized knowledge.

He then recalled some popular science books he had read before. It seemed that Arabic numerals were also spread by Arab merchants during trade between the East and the West. They used these numerals to calculate trade and promoted this system of symbols for the convenience of pricing.

However, in this world, there seems to be no such thing as "long-distance, large-scale trade"—there may be, but ordinary people cannot access it—so there is no need to promote digital symbols.

The end result was that simple symbolic numbers could not be developed. In order to maintain the "technical barrier", symbolic numbers have remained cumbersome, to the point that laymen cannot understand them without special explanation.

"How should I put it... I'm not surprised at all?" Lu Mingfei's lips curled slightly.

But since this world has its own "world customs," Lu Mingfei had to consider whether to spread this Arabic symbol or to make it more complicated and align it with the established practices of the world.

"Forget it, there's no need to go to such lengths." Lu Mingfei clapped his hands. "Alright, you two, since this method is so confidential..."

"Then please keep this a secret for me, at least don't let it spread, okay?"

Ron and Lace nodded almost simultaneously, and it was clear to the naked eye that Ron's attitude toward learning had become more serious.

—At least Rong En won't spout nonsense about "two short sticks representing 2" anymore, which is a good thing.