Please help me solve this.

Question

The problem is:

The ratio of the measurement of an angle to its supplement is 3:5. Find the angle and its supplement

and All I’ve got is:

3x+5x = 180

Answer 1

Let a= angle and s= supplement then a/s =3/5 then a= 3 s/5 a +s =180 3 s/5 +s =180 so 3 s + 5 s = 900 solving for s gives s = 112.5 and using this to solve for a gives a = 67.5 to check take the ratio of the values to find 67.5 /112.5 = .6 as does 3/5.