Answer:
Step-by-step explanation:
Let exterior angle be x
Interior angle = x + 120
Interior angle and exterior angle are linear pair
x +x +120 = 180
2x + 120 = 180
2x = 180 - 120
2x = 60
x = 60/2
x = 30°
No. of sides = 360°/measurement of exterior angle
= 360/30
= 12 sides
