6: Use the formula for sum of interior angles in an n-gon.
10: Use the same formula as in #6, but work backward to solve for n.
17: Find the sum of the known angles by adding and the sum of all the angles by using the formula for sum of interior angles.
25: The sum of the exterior angles of a polygon is 360°.
29: The sum of the exterior angles of a polygon is 360°, and the sum of the interior angles can be found by using the formula.
38: The sum of all the interior angles is n times 165°.
39: The sum of the exterior angles of a polygon is 360°.