我夹克上的纽扣卡住了，我解不开。

The buttons on my jacket are stuck, and I can't ___undo them.

这根绳子缠得这么紧，我解不开这些结。

This rope is so tangled, I can't ___undo the knots.

他费力地想打开那个罐子紧实的盖子。

He struggled to ___undo the tight lid of the jar.