Since the two angles are supplementary, and has a ratio of 1:3, we can say algebraically that
Let x be the measure of angle with a ratio of 1
3x be the measure of angle with a ratio of 3
Solve and we get
Therefore, we have the following
x = 45° (measure of the first angle)
3x = 3(45°) = 135° (measure of the second angle)