Can You Help Us Solve It Then

Huo Beichen's lips curved upwards slightly, his icy cold expression melting into a warm smile.

Eight years ago, she was just like this, always filled with enthusiasm. She often used to say "Don't worry, I'm here!".

She was like a roly-poly toy. No matter what came her way, she never failed to pick herself up the next day with as much vigor as before. He remembered that there was once when the Mathematics teacher was delaying their class with a difficult question although the school session was finished. 

The teacher had said, "If anyone of you can solve this question, all of you can go."

He could not be bothered, and the rest of the class did not know how to answer the question. The teacher then continued to entice them with more rewards.

"If you can answer this question, you won't need to do any homework today."

The girl seated near the door suddenly raised her hand. "Can you help us solve it then?"