Đặt: $\left\{\begin{matrix}n_{Mg}=x\ (mol)\\n_{Al}=y\ (mol)\end{matrix}\right.$
$\Rightarrow 24x+27y=12,6\ \ (1)$
$Mg+2HCl\to MgCl_2+H_2\\ \ \ x\ \xrightarrow{\quad}\ 2x\quad \ \ \xrightarrow{\qquad}\qquad x\ \ \ (mol)$
$2Al+6HCl\to 2AlCl_3+3H_2\\\ \ x\ \ \xrightarrow{\quad} \ 3x\qquad \xrightarrow{\qquad} \quad 1,5x\ \ \ (mol)$
$\sum n_{HCl}=\dfrac{58,8}{36,5}=1,6\ (mol)$
$\Rightarrow 2x+3y=1,6\ \ (2)$
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