Generalising angles in polygons (Part 2)

Maths

If I split a 7 sided shape into 5 triangles, I have done the correct process to find the total interior angles within the shape.

Which of the following WOULD give you the total interior angles within a n-sided polygon?

Which of the following WOULD NOT give you the total interior angles of a n-sided polygon?

The sum of the total interior angles in a 30 sided shape is...

What would be the correct calculation to work out the total sum of the interior angles in a decagon?

How many internal triangles can be formed within a megagon?

How many internal triangles from a distinct point can be formed within an icosagon?

The general formula for working out the total interior angles in a n-sided polygon is...

Using the formula, if I wanted to work out the total interior angles for a 360-sided shape, it would be...