$R=5CM+H\text{ and }5CM+H=12CM+R\text{ and }12CM+R=10CM+H\text{ and }10CM+H=12CM$

$R=0$
$\left(C=0\text{ or }M=0\right)\text{ and }H=0$

$\left\{\begin{matrix}M\in \mathrm{R}\text{, }&C=0\text{ and }R=0\text{ and }H=0\\M=0\text{, }&R=0\text{ and }H=0\end{matrix}\right.$