Question

If the supplement of an angle is two-third of itself ,then its supplement is

Answer 1

( 'x' is not 144 .)
 
The supplement of an angle is (180 - x) .
The problem says that (2/3) of 'x' is equal to (180 - x) .

180 - x = 2/3 x

Multiply each side by 3 :
( Note:  3 x 180 = 540 .)

540 - 3x = 2x

Add 3x to each side:

540 = 5x

Divide each side by 5 :

x = 108° .