You know the first two angles are identical, so let's call them x.
The third angle is 20 more than twice the measure of either angle, which means 2x+20.
The angles of a triangle add up to 180 degrees.
(x)+(x)+(2x+20)=180
4x+20=180
4x=160
x=40 degrees
This means the angle measures equal 40 degrees, 40 degrees, and 100 degrees.