Hey! Here's a cool trick
To find how many degrees are inside of any figure, just see how many triangles can fit inside of it!
This figure can fit 3 traingles, so it is 540°
I got 540° by multiplying the degrees in a triangle (180°) by 3 ...
Now we need to know what x° is, so let's subtract all the numbers they give us from 540°
540° - 87° - 105° - 135° - 92° = 121°
x is 121° !
I hope I helped! Let me know if my explanation is confusing :)