她正在冥思苦想这个数学难题的解法。

She is ___puzzling over how to solve this difficult math problem.

这道数学题太令人困惑了，我完全不知道从哪里开始解答。

This math problem is so ___puzzling that I have no idea where to begin solving it.

她脸上露出了困惑的表情。

She had a ___puzzling expression on her face.