The measure of an exterior angle of a regular polygon is 15°. what is the sum of the measures of the interior angles of the polygon?

First thing you must do is find the number of sides of the polygon.
The sum of all the exterior angles of a polygon is always 360°.
360/15 = 24
The polygon has 24 sides.

The formula for the sum of the interior angles of a polygon is:
180(n - 2)
Where n is the number of sides.

180(24 - 2)
180(22)
3960

The sum of the measure of the interior angles of the polygon is 3960.