Find the value of y if the measures of the interior angles of a convex decagon are 5yº, 5yº, 8yº, 8yº, 9yº, 9yº, 9yº, 9yº, 9yº, and 9yº.
3 sides angle sum 180 degrees
4 sides angle sum = 2*180 degrees
n sides angle sum = (n-2)*180 degrees
so what is the angle sum of a decagon
Once you know that you just have a simple equation to solve.