Question 936404
Two Angles are Supplementary if they add up to 180 degrees
  ley x,y be the supplementary angles
 x+y=180.............eq(1)
 an angle is 20 degrees less than thrice its supplement
   x= 3*y-20
   put x =3y-20 in x+y=180
               (3y-20)+ y =180
                      3y+y-20=180
                   4y-20 = 180
             move -20 to the right
        4y  =180+20
                   4y =200
          divide with 4 on both sides
       {{{ 4y/4=200/4}}}
                y =50
     x= 3*50-20
        =150-20
         =130
so x=130
   y= 50
 ration  x: y  = 130:50
                =13:5
 Result : ratio =13:5