The given system of equations is
[tex]\begin{gathered} x=y\rightarrow(1) \\ x-3y=4\rightarrow(2) \end{gathered}[/tex]
To solve this system by substitution, substitute x in equation (2) by y
[tex]y-3y=4[/tex]
Now add the like terms on the left side
[tex]\begin{gathered} (y-3y)=4 \\ -2y=4 \end{gathered}[/tex]
Divide both sides by -2
[tex]\begin{gathered} \frac{-2y}{-2}=\frac{4}{-2} \\ y=-2 \end{gathered}[/tex]
Substitute the value of y in equation (1) to find x
[tex]x=-2[/tex]
The solution of the system is (-2, -2)
