Both the sum of the third angle in the triangle and x has to be 180deg, as they sum to a half angle;
and the sum of angles in any triangle is 180deg.
We know that x = 180deg - (180deg - 28deg - 32deg) = 180deg - 180deg + 28deg + 32deg = 60deg
Also, note that x is drawn as smaller than a right angle. Unless the picture was made specifically to confuse us, we know that the only answer could be B.
Using the angles we already have we can determine that the missing interior angle is 120 since the interior angles of a triangle add up to 180°. So the missing interior and and the missing exterior angle are supplementary meaning they add up to 180. so 180-120=60°
