(一).It's a deal.就這么辦吧。

This means "agree to your offer." Often the speaker is saying that he and another per. son have agreed on the cost of something that is being bought and sold.

原音重現：

A: If you pay me $7000, I'll sell you the car.
你出7000美元我就把車賣給你。
B: It is a deal. I need to go to the bank first.
成交，我先去下銀行。

(二).A deal's a deal.這是約好的。
This means that a person can't change an agreement that was made. It is a way to say "You have to honor the agreement you made with me."

原音重現：

A: I don't want to buy the car now.
我現在不想買車了。
B： You must. A deal's a deal.
你一定得買，不是約好了嗎？

美劇表達：
We have made the changes you asked for and it's a done deal.
我已經按你的要求改好了，就照約定的做吧