How much degrees is a pentagon?

The sum of internal angles of a shape is given by the equation 180(n-2) where n is the number of sides. For a pentagon, which has 5 sides, this would be 180x3 = 540. The sum of external angles of a shape is given by (180-(x/n))n where n is the number of sides and x is the sum of internal angles. For a pentagon, this would be 5x(180-540/5) = 360