A regular polygon has interior angles of 168. How many sides does it have?

##360 div 12 = 30## sides
The only number that stays the same for the angles of all polygons is that the sum of the exterior angles is 360.
If you know the size of an exterior angle##(theta)## in a regular polygon you can find the number of sides:
##360 div theta = ##number of sides
If you know the number of sides ##(n)## you can find the size of each exterior angle of a regular polygon.
##360 div n = theta##
Interior angle ##168 rarr exterior angle = 180-168 = 12##
##360 div 12 = 30## sides.