Polygon Basics

Answer: 152.31

To find the interior angle of a polygon, you first take the number of sides, "n", and subtract 2: $x=n-2$ . Multiply the result by 180 (You are fitting x triangles into the polygon, and funding the sum of all angles): $s=x\cdot180$ . Then, divide s by n: $\frac{s}{n}$ .

For our 13-gon: $11=13-2$ $1980=11\cdot180$ $\frac{1980}{13}\approx \boxed{152.31}$