He wondered if he might have a piece of cake.

他想知道他是否可以吃一块糕。

How about a piece of cake?

来一块蛋糕吧？

We need not have worried about the math exam. It was a piece of cake.

我们本不必担心数学考试，实际上很容易。

Oh, you'll do it. It's a piece of cake.

噢，你办得到的，这不费吹灰之力。