Supplementary angles are two angles whose sum is equal to 180, therefore:
if the ratio of the two angles is 1:8, then
180 = 1x + 8x
(1x, or x is the value of the measure of the smaller angle and 8x is the value of the measure of the larger angle)
180 = 9x
180/9 = 9x/9
20 = x
if the ratio of the two angles is 3:5, then
180 = 3x + 5x
(3x is the value of the measure of the smaller angle and 5x is the value of the measure of the larger angle)
180 = 8x
180/8 = 8x/8
22.5 = x
3x = 3*22.5
3x = 67.5