12 sided regular polygon has interior angles = 150 degrees
the general formula is (n-2)180 = sum of interior angles
divide by n to get one interior angle
(n-2)180/n = 150
(n-2)180 = 150n
180n-360 = 150n
180n-150n = 360
30n =360
n= 360/30 = 12
n = 12 = number of sides of a polygon with a 150 degree interior angle