You can put this solution on YOUR website! The supplement of an angle is 60 degrees less than twice the supplement of the complement of the angle.
Let x = the angle
then
90-x = complement of angle
180-x = supplement of angle
180-(90-x) = 90+x = supplement of complement of angle
.
180-x = 2(90+x) - 60
180-x = 180+2x -60
-x = 2x -60
-x+60 = 2x
60 = 3x
20 degrees = x