Let n = one of the angles
Let 2n -30 = the other
n+ 2n -30 =90⁰ (because they are complementary)
Combine like terms -- 3n -30 = 90
Add 30 to both sides of the equation
3n=120°
Divide both sides by 3 and n=40° 2n -30 = 80 -30 = 50°
So one angle is 40° and the other is 50° and those angles are complementary.