Answer:
x = 140
Explanation:
Using the exterior angle rule ( an exterior angle of a triangle is equal to the opposite interior angles of a triangle )
x is the interior angle and the given angles ( 50 and 90 ) are the opposite interior angles
So
x = 50 + 90
50 + 90 = 140
x = 140
Note: there is a right angle ( indicated by the little square. A right angle has a measure of 90 degrees so that's where the 90 came from)