9514 1404 393
Answer:
126°
Explanation:
To find the exterior angle, we need to know one of the acute angles. Those are found using the fact that they are complementary.
(5x -6) +(3x) = 90
8x = 96 . . . . . . . . . . . add 6, collect terms
x = 12 . . . . . . . . . . . . . divide by 8
3x° = 3·12° = 36° . . . . . . find the "remote" acute angle
exterior angle = 90° +36°
exterior angle = 126°
__
The exterior angle is the supplement of the one marked (5x-6)°. It is also the sum of the two remote interior angles, 90° and 3x°. Being lazy, we figure that 90 +3·12 is easier to compute than 180 - (5·12 -6). Either way, the exterior angle is 126°.