Hello!
The angle is a straight angle, which measures 180°.
One angle is a right angle, which measures 90°, while the other angle measures 30°.
90 + 30 = 120
That means x = 180 - 120. To find x, subtract 120 from 180
180 - 120 = 60
[tex]\framebox{x = 60 \°}[/tex]