I'm just going to straight up tell you the formula ffor trial and error. I don't know any smarter way because I'm not smart. :P a/180+2=n. N is how many sides, and a is the amount of angles. I got this from a=(n-2)/180. So you do... 360 also 120*3. (360+150*n)/180+2. Solve this multiple times until you get a whole number. BTW... It's 9 sides. (360+150*6)/180+2=9.
