Answer:
x = 6
Step-by-step explanation:
Using the exterior angle theorem
The exterior angle of a triangle is equal to the sum of the 2 opposite interior angles.
79° is an exterior angle of the triangle , then
8x - 13 + 9x - 10 = 79
17x - 23 = 79 ( add 23 to both sides )
17x = 102 ( divide both sides by 17 )
x = 6
