`a)`

`Hh:Mg:x(mol);Zn:y(mol);Al:z(mol)`

`24x+65y+27z=19,46(1)`

`m_{Mg}=m_{Al}<=>24x=27y(2)`

`Mg+2HCl->MgCl_2+H_2`

`Zn+2HCl->ZnCl_2+H_2`

`2Al+6HCl->2AlCl_3+3H_2`

`->n_{H_2}=x+y+1,5z={18,0967}/{24,79}=0,73(3)`

`(1)(2)(3)->x=0,27;y=0,1;z=0,24`

`m_{Mg}=m_{Al}=0,27.24=6,48(g)`

`m_{Zn}=0,1.65=6,5(g)`

`b)`

`n_{HCl\ pu}=2n_{H_2}=1,46(mol)`

`n_{HCl\ du}=1,46.10\%=0,146(mol)`

`->V_{dd\ HCl\ bd}={0,146+1,46}/{2}=0,803(L)=803(mL)`