Quadrilaterals interior angles and exterior angles

Question

How many sides does a polygon have if the measure of each interior angle is 8 times the measure of each exterior angle?

Answer 1

n represents the number of sides

360 / n represents the size of each exterior angle

(n - 2)(180) / n represents the size of each interior angle

(n- 2)(180) / n = 8(360 / n)

(n - 2)(180) = 8(360)

(n - 2) = 8(2)

n - 2 = 16

n = 18