You can put this solution on YOUR website! Recall that the sum of the angles of a n-gon is . Plug in the case of n=13 to get for the angular sum of 1980.
Since it is regular, each of the angles are equivalent. If they are all equivalent, then the value of one is the sum divided by the number of angles, or
The angles are roughly 152.307692 or 152, as 1980 divided by 13 is already simplified