For a nine-sided enclosed object, a nonagaon, the equation would be 360 degrees divided by 9. That will provide you with the answer.
The formula for an exterior angle is 180-(180/n)(n-2) where n is the number of sides. For a nonagon the number of sides is 9. Plugging this into the equation gives: 180-(180/9)(9-2) =180-(20)(7) =40 So the exterior angles of a regular nonagon will measure 40 degrees.