Question

How do you work out interior angles?

Answer 1

N = number of sides in the shape.

The formula I know it from is; n - 2 x 180

For example; 7 - 2 [5] x 180 = 900

So, a heptagon's interior angles should add up to 900. 

Hope this helped! :)

Answer 2

If 2 lines are congruent alternate interior angles are congruent