[tex]\begin{gathered} 3x+4y=18 \\ 3x+y=-3 \\ \\ \text{After subtracting both equations we get} \\ 3y=21 \\ \frac{3y}{3}=\frac{21}{3} \\ y=7 \\ \\ \text{Put the value of Y on one of the initial equations} \\ 6x+2(7)=-6 \\ 6x+14=-6 \\ 6x+14(-14)=-6(-14) \\ 6x=-20 \\ \frac{6x}{6}=\frac{-20}{6} \\ x=-\frac{10}{3} \end{gathered}[/tex]