假如你是Mr. liu.阅读下面一封信，请根据信件内容给Tom写一封70词左右的回信。
Dear Mr. Liu:
I failed my math again. I think I’m hard-working and I listen to the teachers carefully in class. I always get nervous while taking an exam. If my mom knows it, she will be mad at me. What should I do? Could you give me some good advice?
Sincerely,
Tom
Dear Tom:
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Sincerely
Mr Liu
