I'm assuming the question is referring to a regular pentagon where all the sides and angles are equal, because otherwise, I would need more information (such as lengths of sides, meausures of angle, diagram, etc) to be able to solve this.
180(n-2)
n = 5 because a pentagon has 5 sides
5 - 2 = 3
180 * 3 = 540
divide 540 by 5 (again, because a pentagon has 5 sides)
540 ÷ 5 = 108
The sum of all the interior angles together is 540 degrees, and the measure of just one of them is 108 degrees