It is an isosceles triangle which means two sides are the same and when two sides are the same then the two angles are the same. The bottom one is 80 degrees so the other angle equals to 80 degrees Add both 80 degrees angle 80+80= 160 In a triangle all the angles equal to 180, so now you subtract 180-160 = 20 The angles are 80, 80 ,20 The 20 is on top and the two 80 are on the bottom
