Question

An angle measures 20° less than the measure of its supplementary angle. What is the measure of each angle?

Answer 1

Answer: 80 degrees and 100 degrees

Work Shown

Let x and y be the two angles

The two angles add to 180 since they are supplementary

x+y = 180

Another equation is y = x-20 to represent angle y being 20 degrees less than angle x.

Apply substitution to solve

x+y = 180

x+x-20 = 180

2x-20 = 180

2x = 180+20

2x = 200

x = 200/2

x = 100 degrees is the measure of one angle

y = x-20 = 100-20 = 80 degrees is the measure of the other angle