Consider the equation x-y=4 and express y in terms of x.
[tex]\begin{gathered} x-y=4 \\ y=x-4 \end{gathered}[/tex]Put x-4 for y in the equation 3x+y=0 implies,
[tex]\begin{gathered} 3x+x-4=0 \\ 4x=4 \\ x=1 \end{gathered}[/tex]The, the value of y is,
[tex]\begin{gathered} 1-y=4 \\ y=-3 \end{gathered}[/tex]Thus, x=1 and y=-3
