Answer:
measure of exterior angle at C = 160°
Step-by-step explanation:
An exterior angle of a triangle equals the sum of the two remote interior angles
A and B are the remote interior angles. So,
m∠A + m∠B = measure of exterior angle at C
5x - 10 + 12x = 16x
17x - 10 = 16x
x = 10
measure of exterior angle at C = 16x = 16(10) = 160°