The angle 1 and the side equal to 72° together equal 180. 72 + x = 180 using the subtraction property of equality we can conclude that x = 108.
Side 2 is parallel with 72° making them equal and Side 3 is parallel with 108° making them equal.
Side 1 = 108°
Side 2 = 72°
Side 3 = 108°