The formula for volume is Length x width x height.
Bottom: 18 * 12 * 8 = 1728 cubic centimeters.
Middle: 12 * 8 * 6 = 576 cubic centimeters.
Top = 4 *4*4 = 64 cubic centimeters.
Total: 1728 + 576 + 64 = 2368 cubic centimeters.
Well, the amount of degrees is 1,980, so plug that in so that the equation is 1980 = (n-2)180. Then, do order of operations. Divide 1980/180, which is 11. Then, just add 2. So, the polygon has 13 sides.