SOLUTION
From the first equation, we make x the subject and put into the second equation. This equation is
[tex]-x+2y=-6[/tex]
Making x the subject, we have
[tex]\begin{gathered} -x+2y=-6 \\ -x=-2y-6 \\ \text{dividng through by -1 we have } \\ \frac{-x}{-1}=\frac{-(2y+6)}{-1} \\ \\ x=2y+6 \end{gathered}[/tex]
So we substitute 2y + 6
