Question 92156
here we have 2 equations x+y=12  ...........(1)
    and y=2x ..........(2)
  now we can replace the value of y of equation (1) by 2x 
so we have x+2x =12
or 3x =12
or x = 12/3= 4

we know from equation (2) that y = 2x
therefore value of y = 2*4= 8


 ans ..... x = 4 and y = 8