The sum of the interior angles in a triangle is 180.
We can find what one of angles are. Since the sum of two angles are 80, that leaves the third angle.
180-80=100
This means one angle equals 100.
We can make an equation to find what the two angles are. Let's have x as the smaller angle.
x+x+20=80; since their difference is 20.
2x+20=80; let's subtact 20.
2x=60; now divide by 2.
x=30
Since the smaller angle of the two is 30, the other is 50.
So, the angles of the triangle are 30°, 50°, and 100°