In step 1, y was made the subject of the second equation to get:
y=5x-4
To proceed, the next step is to substitute the expression into the other equation, not the equation we solved for y.
8x+2y=-12
8x+2(5x-4)=-12
8x+10x-8=-12
18x=-12+8
18x=-4
x=-
x=
answer= the value of x is -2/9