Question 442524
Let's call this angle x. The supplement of x is 180-x by definition.

3*(180-x) - 20 = x

540 - 3x - 20 = x
520 = 4x
x= 130

Let's check this:

If x is 130, then the supplement of x is 180-130 = 50.
Three times the supplement of x is 3*50 = 150.
And 20 less than that is 150-20 = 130.  

So the angle is {{{130}}}.