If you're trying to find the value of ∠UVX (∠XVU), your answer is 30°.
Why is this the answer?:
To find the value of the missing angle, you need to subtract.
In this case, ∠UVW (∠WUV) is 72°.
We're also given the information that ∠XVW (∠WVX) is 42°.
Therefore, if we subtract 72 - 42, we get 30.
But the degree sign back on: Your answer is 30°!
Hope this helps you! :)