To solve this, we will use the Exterior Angle of a Triangle Theorem, which states that the exterior angles in a triangle are congruent to the 2 interior remote angles.
Therefore:
17x-1 = 84 + 7x+5.
• The exterior angle = the 2 remote interior angles.
17x-1+1=84+7x+5+1
17x = 84+7x+6
17x-7x = 84+7x-7x+6
10x = 84+6
10x = 90
10x/10 = 90/10
x = 9
