他怎么那么受欢迎，我百思不得其解。

It's always surprised me how popular he is.

《牛津词典》

我心中有一个疑团，百思不得其解。

I have in mind some doubts which really puzzle me.

《新英汉大辞典》

所有这一切可能会让你百思不得其解。

All this might have you scratching your head.

youdao

Economists when researching it all over the place, but I feel a lot has to do with monetary policy.

经济学家常百思不得其解，但我感觉经济与货币政策有很大干系。

斯坦福公开课 - 经济学课程节选

Perhaps you too have felt wine talons grip you unexpectedly sometime and carry you aloft.

可能你也觉得这句有时很出乎人意料,让人百思不得其解。

耶鲁公开课 - 现代诗歌课程节选

Next week, social thought and social behavior, mysteries; basically, a series of topics that don't fit anywhere in the course and really make psychologists scratch their heads.

下节课我们将会讲社会思想,社会行为，神话;,基本上这一连串的话题,在本课程中属于杂七杂八的,而且让心理学家百思不得其解的。

耶鲁公开课 - 心理学导论课程节选