Question

an angle is 30 degree less than two times its supplement find the angle

Answer 1

x+y=180
x=2y-30

2y-x=30

add equation 1 and 3

3y=210
y equals 70°
and x equals 110°

Answer 2

angle + supplement = 180, hope you know that
Supplement = x
angle = 2x - 30
so
2x - 30 + x = 180
3x - 30 = 180
3x = 210
x = 70
So supplement is 70
180-70=110
so the angle is 110