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