Supplementary angles are angles which have a sum equal to 180 degrees. Let us say that the angles are x and y therefore:
x + y = 180
Assuming that x is the larger angle, so the difference is:
x – y = 30
Combining the two equations:
x + y + x – y = 180 + 30
2 x = 210
x = 105 degrees
y = 75 degrees
The two angles are 105° and 75°