\left \{ {{12x-7y=2} \atop {12x-15y=18}} \right. => \left \{ {{12x-7y=2} \atop {12x-15y-12x+7y=18-2}} \right. " alt="\left \{ {{12x-7y=2} \atop {4x-5y=6}} \right. => \left \{ {{12x-7y=2} \atop {12x-15y=18}} \right. => \left \{ {{12x-7y=2} \atop {12x-15y-12x+7y=18-2}} \right. " align="absmiddle" class="latex-formula">
\left \{ {{12x-7y=2} \atop {y=-2}} \right. => \left \{ {{12x-7(-2)=2} \atop {y=-2}} \right. =>\left \{ {{12x=-12} \atop {y=-2}} \right. " alt="\left \{ {{12x-7y=2} \atop {-8y=16}} \right. =>\left \{ {{12x-7y=2} \atop {y=-2}} \right. => \left \{ {{12x-7(-2)=2} \atop {y=-2}} \right. =>\left \{ {{12x=-12} \atop {y=-2}} \right. " align="absmiddle" class="latex-formula">
