x = the angle
180 - x = supplement of the angle {supplementary angles add up t0 180}
90 - x = complement of angle {complementary angles add up to 90}
180 - x = 6(90 - x) {supplement is 6 times the complement}
180 - x = 540 - 6x {used distributive property}
-x = 360 - 6x {subtracted 180 from both sides}
5x = 360 {added 6x to both sides}
x = 72