[tex]-3(m-2n)=12\ \ \ \ \ |:(-3)\\\\m-2n=-4\\\\\text{Solve for m:}\\\\m-2n=-4\ \ \ \ |+2n\\\\\boxed{m=2n-4,\ n\in\mathbb{R}}\\\\\text{Solve for n:}\\\\m-2n=-4\ \ \ \ |-m\\\\-2n=-m-4\ \ \ \ |:(-2)\\\\\boxed{n=\dfrac{m+4}{2},\ m\in\mathbb{R}}[/tex]
