轻而易举的事情。

It means something that is easy to do.

它意思是有些事情非常容易做到。

Aaron got a perfect score on his test.

亚伦在这次考试中获得了非常有意的成绩。

It was a piece of cake for him.

这对于他来说太简单了。

Math is a difficult subject but English is a piece of cake for me.

数学是一门很难的学科，但对我来说却易如反掌。

I can finish the project in one hour.

我可以在一个小时内完成这个项目。

It will be a piece of cake.

这是小菜一碟。