Answer:
s = 63°
Step-by-step explanation:
the exterior angle of a triangle is equal to the sum of the 2 opposite interior angles.
s + 50 is an exterior angle of the triangle , then
s + 50 = s - 13 + s
s + 50 = 2s - 13 ( subtract s from both sides )
50 = s - 13 ( add 13 to both sides )
63 = s
