Query on Geometry tickbox quiz 10

I have a query pertaining to Geometry tickbox quiz 10. In question number 11 you have taken the formula for the sum of interior angles is (n-2)x180/n, however in the lesson video it is just (n-2)x180.

Not the sum, but something related. What does dividing by n do?

Be careful because it says “its interior angle” and not the sum of the interior angles.