冥思苦想

I puzzled over the problem for ages before the light suddenly dawned on me.

我对这个问题了很久才豁然开朗。

As people grow older, they begin to ruminate on the uncertainty of life.

随着年龄的增长，人们开始对生活的变化。

He puzzled his brains to find an answer.

寻求答案。