The sum of the interior angles of a convex n-sided polygon can be found using the formula:

360 (n - 2)

180 (n - 2)

180n - 2

360n

It is: 180 (n-2)

For example, the sum of the interior angles of a triangle is 180 degrees.

The quadrilateral can be cut into two triangle so the sum of the interior angles of a quadrilateral is 180*2=180 * (4-2)

The pentagon can be cut into three triangle so the sum of the interior angles of a pentagon is: 180*3=180 * (5-2)

The hexagon can be cut into four triangle so the sum of the interior angles of a hexagon is: 180*4=180 * (6-2)