1. The formula you used determines thesumof all interior angles of a polygon. The value of one single interior angle is calculated by

where n is the number of vertices of the polygon.

2. Let n denote the number of vertices of the congruent polygons and k the number of vertices of the other one then you'll get:

Simplify this equation and you'll get

3. The perimeter of the 3 polygons is

4. I'll leave the rest for you.