Supplementary means that the two angles add up to 180 degrees. If mTUV= 75, and mMNO = (5x) we can make an equation with them 75 + (5x) = 180 subtract 75 from both sides (5x) = 105 now divide both sides by 5 to isolate the x x = 21 now plug the value for x, 21, back into the original This means that m MNO = 5(21) do the multiplication That equals 105 degrees.
Just to check plug it into the supplementary angle equation 180 ? 105 + 75 180 = 180