SUM OF THE INTERIOR ANGLES OF A TRIANGLE #3 in each of the triangles below. The Triangle Sum Theorem states that the interior angles of a 180. Your first step should be to set up an equation where the sum of the angles adds up to or x, then plug that value back in to the expressions to find the measure of the missing angles. 2) A B 3) C 4) 5x 4x X x+52 3x x+60 A x+8 A 4x C B B LA = LA = LA = LB = X = LB = X= LB = LC = ZC = LC = B A B 8 A 6 7) 2x+30 2x+25 2x 3x