June 31, 12:00 p.m. Metro Line 11 Disney Station

Hezhi and Yang Fan hugged Heli and ran onto the subway. "Fortunately, there is still a seat, so that Heli can lie down and rest for a while." Hezhi quickly sat down, lay Heli's head on her lap, stroked Heli's head with his hand, and said, "Good brother, you are already very strong!"

After more than a dozen stops of the subway, Heli's eyes slowly opened and he looked around.

“，.... Is this on the subway?"

"Heli! You were so brave that you managed to get the map!" Yang Fan said excitedly. "Great! It seems that we have succeeded in a third of this expedition. Hurley said, a small smile on his face.

"However, it's only a third of what we've done, and we're still two-thirds of the way through." Yang Fan sighed, and then said, "We are still a few steps away from success, let me think about it........

"I also have to go to Yu Garden to get the "Nine Chapters of Arithmetic" and then calculate the yuan-order equation, and finally use the key to open the top of the financial center and get the coordinate axis." As soon as Yang Fan's voice fell, the subway arrived at the station they wanted to transfer.

Line 10 Yuyuan Garden Station

When they arrived at Yu Garden, they desperately squeezed through the crowd, and He Li was a little nervous: "There are still so many people in Yu Garden, will it be as difficult to find "Nine Chapters of Arithmetic" as it is to find a map?" Probably not! "Nine Chapters of Arithmetic" is at the location of the Jiuqu Bridge, I have checked. ”

They walked and walked, and finally came to the Jiuqu Bridge, and saw a small house next to the Jiuqu Bridge, which sold ancient books. Walking into the bookstore, Yang Fan looked at the bookshelf and read softly: "The Analects", "Mencius", "University", "The Mean", "Di Zi Gui", "Three Character Classic" next to He Li and He Zhi are also looking carefully. "Journey to the West", "Romance of the Three Kingdoms", "Zhou Yi", "Spring and Autumn", "Book of Rites"

"Pythagorean square diagram", "Fixation".... Wait a minute! "Nine Chapters of Arithmetic"?" Hitch found this book

The "Nine Chapters of Arithmetic", which has been hidden for thousands of years, surprised them. He Li and Yang Fan asked in unison, "How did you find out the Nine Chapters of Arithmetic?"

"Look up." Hezhi pointed to the ceiling and said, "Here are ancient Chinese mathematical works, and all ancient mathematical works are placed here." After speaking, Hezhi took out this book of "Nine Chapters of Arithmetic" and handed it to the cashier. The cashier looked at it and asked, "Excuse me, are you a math geek?" That's right, I'm a born mathematician. Any questions?" Hezhi said, and the cashier smiled and said, "It's okay! Do you need axes? I have a lot of them here, 16 o'clock, 32 o'clock, 64 o'clock....

"Looks like you've guessed it." He Li whispered to Yang Fan.

"I want the axis at the top of the financial center." Hezhi continued, but the cashier's face suddenly changed, and he said, "The top of the financial center? It is not a place that ordinary people can enter casually, because there are many rational elements there, which is the center that supports the operation of the whole Shanghai, although the coordinate axes are not linked together, but the coordinate axes are strictly controlled. If the coordinate axis is removed, the whole of Shanghai will be in a panic!"

"What? Why is this happening? You don't know we're here to stop things from happening!" Hurley was anxious again.

"Okay, but I'm not forcing you, because I've read the newspapers and it's been so serious. So, I'll give you the key, and you'll take another piece of A4 paper as a support. Also, be extra careful!" After saying that, the cashier handed the key to Hezhi.