The angles inside a triangle always sum to 180°. We already have a 32° angle and a 90° - totalling 122° - and when we add x°, we'd like the sum to be 180°. So x must be 180 - 122 = 58.
The total should be 180 degrees. We know the the top angle is 32 degrees and the bottom left is 90 degrees because it has a square there. So 32+90=122. If we subtract 122 from 180 we are left with 58 degrees so x=58
