Question

one angle is 2/3 of its supplementary angle is 180 degree. find its magnitude?

Answer 1

let one angle is x then its supplementary angle is 2x/3
x + 2x/3 = 180
5x/3 = 180
x = 108
supplementary angle is 2*108/3 = 72

Answer 2

The measure of an angle is 2/3 the measure of its supplement. Find the measure 
of the angle and its supplement. 
let one angle be = x
then its supplement =( 180-x) 
according to the sum we have 
x = 2/3 (180-x) 
x = 2/3*180 - 2/3*x 
x = 2*60-2/3x 
x+2/3*x= 120-2/3*x+2/3*x 
3x+2x/3 = 120 
5x/3*3= 120*3 
5x = 360 
5x/5 = 360/5 
x = 72 degrees 
the supplement angle = 180-72 = 108 degrees