Supplementary angles by definition means the sum is 180. From that knowledge we can write up some equations. Let angle 1 = x, and angle 2 = y
x + y = 180
"The larger of two supplementary angles measures 20° less than four times the measure of the smaller angle" (Let x be the larger angle) x+20 = 4y
Since there are two different equations, and two variables, this means we have a set of simultaneous equations. We can solve this via the substitution method or the elimination method.
I choose to solve it via the substitution method cause of personal preference. x + y = 180 => x = 180- y x+20 = 4y => x = 4y - 20 Make them equal each other.. 180 - y = 4y - 20 200 = 5y 40 = y Now that we know y we can sub it into any equation to find x x + 20 = 4y x + 20 = 4(40) x + 20 = 160 x = 140 So the angles are 40° and 140°
