The interior angles of a convex polygon are in arithmetic progression. The smallest angle is 120 degrees and the common difference is 5 degrees. Find the number of sides of the polygon.
+36916 The xterior angles sum to 360 degrees
180 -120 + 180 - 125 + 180 - 130 + 180 - 135 + 180 - 140 +
180 - 145 + 180 - 150 + 185 - 155 + 180 - 160 = 360 9 sides
