If the measure of an exterior angle of a regular polygon is 24, how many sides does the polygon have?

If the exterior angle = 24 the interior angle = 180 - 24 = 156 

then we have a rule which is : 
the interir angle of a regular polygon =(n-2) × 180° / n , where n is the number of side 
so 156 = (n-2) × 180° / n 
156n = 180n - 360 
360 = (180-156) n 
360 = 24 n 
15 = n  hope it help
so number of sides = 15

Ithink the answer is last one.