Replace one of the equations into the other leaving only x as a variable
[tex]3x=x-4[/tex]solve the equation for x
[tex]\begin{gathered} 3x-x=-4 \\ 2x=-4 \\ x=\frac{-4}{2} \\ x=-2 \end{gathered}[/tex]replace the x into one of the first two equations
[tex]\begin{gathered} y=(x)-4 \\ y=-2-4 \\ y=-6 \end{gathered}[/tex]the solution for the system of equations is (-2,-6)