What's the sum of the measures of the interior angles of a convex nanogon

You need to find the measure of one interior angle. You must find the value of the exterior angle and subtract that from 180 degrees (they are supplementary:_/_). The formula to find the value of an exterior angle is 360/n where n is the amount of sides

360/9=40

subtract from 180

180-40=140

multiply 9 (there is 9 angles)

140*9=1260 degrees