Ever since she returned the problem book to Dean Gu, Meng Zhao had been waiting for his invitation, but she hadn't heard from him for several days. She thought Dean Gu had forgotten about her until last night when Shen Qinghe brought an invitation, saying that Dean Gu invited her to the academy for a chat.

That day, Meng Zhao got up and washed up in the morning. When choosing clothes, she deliberately chose a simple one, which made her look more composed than usual. Before leaving, she checked again and again to make sure she had brought the invitation. Then she took the carriage to the academy.

As soon as Meng Zhao arrived at the academy gate, she was stunned by the ancient cypress tree. Its trunk was so thick that it would take two people to hug it, and it was estimated to be over a hundred years old. Looking up, the four powerful characters "Mingde Academy" hung high above the gate, revealing a sense of solemnity. Meng Zhao subconsciously straightened her robes and was about to go in when a round-faced boy at the gate came to greet her.

"Is this Lady Meng?"

Meng Zhao nodded, and the young man smiled, revealing a pair of dimples: "Dean Gu and the others have been waiting for a long time. Please follow me."

"Them?" Could there be others besides Dean Gu? Meng Zhao didn't dare to ask too many questions and followed the boy through the courtyards.

Along the way, the boy introduced the various sights as if they were his own treasures: "This is the library... that's where the students read in the morning..."

Upon reaching a secluded courtyard, the young man stopped and bowed, saying, "Dean Gu is inside. Please, Madam Meng."

Meng Zhao straightened her clothes and led Huang Cui into the courtyard. The next moment, she was so surprised that she almost bit her tongue. There were seven or eight people standing or sitting in the courtyard. The youngest of them looked to be over thirty years old, and two of them had white hair and beards. They were talking in hushed tones while holding teacups.

Hearing the footsteps, everyone's eyes turned to them. Meng Zhao felt a tightness in her back. One of the women spoke up with a smile, "This must be the elder sister that Hua Zhang often mentions, Madam Meng?"

She was in her early thirties, with a kind face and an air of scholarly refinement. Meng Zhao relaxed slightly and nodded, "It's me. May I ask who you are?"

The woman smiled even more broadly upon seeing this. "My surname is Zhuge, and I am a mathematics teacher at Mingde Academy. I heard you were coming today, so I specially asked the horse riding instructor to change my class time. I'm so glad to finally meet you."

Facing a group of solemn-faced older men, Meng Zhao instinctively felt closer to the female tutor. An elderly man with graying hair and beard, sitting nearby, stood up. "Madam Meng," he said, "I'm truly sorry. I only intended to invite you to discuss mathematics privately, but these old fellows got wind of it and insisted on coming along for the fun." He then glared at the group. "Did I scare you?"

It seems this person is Gu Chongshan, the dean of Mingde Academy. Meng Zhao shook his head, "Dean Gu, you flatter me. Mathematics is a profound and complex subject, and it is precisely through the collective wisdom of all that we can make progress. It is my honor to have the opportunity to discuss this with you seniors today."

Her words were neither humble nor arrogant, displaying both modesty and integrity. A hint of admiration flashed in Gu Chongshan's eyes. He stroked his beard, about to speak, when a middle-aged man dressed in an indigo robe could no longer contain himself and hurriedly said, "Stop being so polite, Madam Meng, come and take a look. We've been looking at this problem for a long time. Although we know your answer is correct, we still can't understand your solution. Please help us figure it out."

Seeing this, Meng Zhao couldn't help but smile. Although this gentleman was over forty, he was like a young student. Meng Zhao no longer stood on ceremony and walked into the crowd to look at the question with them: "There is an unknown number of objects. When counted in groups of three, there are two left over. When counted in groups of five, there are three left over. When counted in groups of seven, there are two left over. How many objects are there?"

The question is: there is a bunch of things whose exact quantity is unknown, but we know that they are grouped in sets of three with two left over, in sets of five with three left over, and in sets of seven with two left over. The question is: how many are there in total?

This is a relatively simple congruence problem, so Meng Zhao's solution steps are also written in a slightly simple way. However, since it is a discussion, how can she be the only one talking? Everyone should talk together. So Meng Zhao asked, "I think everyone has seen this problem before. I would like to ask how everyone solved it before."

The anxious man from before said, "We used to have a method, which was to first list all the numbers that leave a remainder of 2 when divided by three, such as 5, 8, 11, 14, 17, 20, 23..."

Then select from the above numbers that leave a remainder of 3 after five, for example, 8, 23, 38, 53, 68…

Finally, select the numbers that leave two when counted seven times, for example, 23, 128, 233...

The final result showed that the smallest number was 23.

Meng Zhao nodded slightly, "That's right, it's exactly as I calculated."

The gentleman who asked the question frowned, stroked his beard, and sighed, "The result is correct, but we always spend a long time calculating such problems. Moreover, the larger the number, the more difficult it becomes. It's really annoying to calculate."

Pointing to the crisscrossing lines on the paper, she said in bewilderment, "Madam Meng has drawn many strange things in the steps of solving this problem. We really can't figure out the mystery behind them. We hope you will kindly enlighten us."

That will naturally be discussed, but before I begin, I have a few questions to ask: "Do all of you gentlemen recognize the numbers I have written on this paper?"

Master Zhuge pointed to the booklet and said, "Is that what Lady Meng was referring to—those winding, seemingly simple characters?"

Meng Zhao nodded. "Yes, I found these in some books from the Western Regions. I discovered that although these numbers are not very precise, they are much simpler to write than Chinese characters, so I started using them."

Master Zhuge chuckled upon hearing this, “As early as when we saw the booklet you gave to Qingze and Qingyu, we asked them about it, and Huazhang also came to explain it to us. Now we can match it up.”

Meng Zhao breathed a sigh of relief. That was fine, but he was also a little annoyed. He should have brought a blackboard. But there was no other way now. He could only spread out a large sheet of paper on the table and say, "My problem-solving approach is a little different from yours. I am not using the trial and error method, but setting up an unknown."