$n_{O_2}= 0,35 mol$
$2Mg+O_2\to 2MgO$
$2Zn+O_2\to 2ZnO$
$4Al+3O_2\to 2Al_2O_3$
$\Rightarrow n_{O_2}= 0,5n_{Mg}+0,5n_{Zn}+0,75n_{Al}= 0,35 mol$
$Mg+2HCl\to MgCl_2+H_2$
$Zn+2HCl\to ZnCl_2+H_2$
$2Al+6HCl\to 2AlCl_3+3H_2$
$\Rightarrow n_{HCl}= 2n_{Mg}+ 2n_{Zn}+3n_{Al}$
$\Leftrightarrow 0,25n_{HCl}= 0,5n_{Mg}+0,5n_{Zn}+0,75n_{Al}=0,35$
$\Leftrightarrow n_{HCl}=1,4 mol$
$m=1,4.36,5:14,6\%= 350g$