Answer:
x = 7
Explanation:
the exterior angle of a triangle is equal to the sum of the 2 opposite interior angles.
(19x + 3)° is an exterior angle of the triangle , then
19x + 3 = 9x + 16 + 6x + 15 ( simplify right side )
19x + 3 = 15x + 31 ( subtract 15x from both sides )
4x + 3 = 31 ( subtract 3 from both sides )
4x = 28 ( divide both sides by 4 )
x = 7