what am I doing wrong Solutionhere given equation X2y 9 y

what am I doing wrong ?

here given equation X+2y = 9 ; y= -2x

substitute the y= (-2x) in equation X+2y = 9

then the equation will be X+2(-2X) = 9

===> X-4X = 9

-3X = 9

therefore - X = 9/3

multiply negative sign (-) with both sides then we get.

X = - 3 .

I think now it is clear for you. If you have doubts please comment .