P-5:pay sb. back in sb's own coin 以牙还牙
A:John beat me black and blue yesterday.
A:约翰把我打得鼻青脸肿。
B:Why?
B:为什么？
A:Because I told the teacher about his cheating on the exam.
A：因为我告诉老师他考试作弊。
B:He goes too far.
B:他太过分了。
A:I'm determined to pay him back in his own coin.
A:我想以牙还牙。
B:You can never do that.
B：你千万别那么样。
