the formula s= (n-2) * 180 can be used to find the sum of the interior angles of a polygon with n sides. Which formula can be used to find the number of sides a polygon has?

it would open into a square depending on the type of envelope i’m not sure about the second part

l' jhl jje f id bid b e iueb v jhdvb vh ei uf djbduv evb                                                                                                                                   8gfdgsfhjk.,l/ uh   dv eb b                            

if i'm not wrong, i would say that the third angle has (72) because the three sides of all triangles have 180 degrees and if we subtract 180 - 62 - 40 = (72) / but i'm not sure about 40 yd.