Sum of the interior angles of a pentagon is 720 degrees. Sum of two angles that form a bisected line is 180 degrees. So interior angles going clockwise are 138 degrees. 128 degrees. 119 degrees. 180- 2*t degrees. And 180 - 3*t degrees. So sum of angles is: 138+128+119+(180 - 2*t) + (180 - 3*t) = 720
