(someone) is stumped

Being "stumped" means that you don't know the answer to something, and you don't have any more ideas about how to solve it. For example, you might say this to another student about your math homework:

A: Do you know how to solve number 15?

B: No, I'm stumped.

This idiom doesn't sound too negative. It is fine to use in either formal or casual situations.

This phrase appears in these lessons: