a)

$2Al+6HCl\to 2AlC{l}_3+3H_2\uparrow$  

b)

$Zn+H_{2}S{O}_4\to ZnS{O}_4+H_2\uparrow$  

c)

$3Fe+2H_{3}P{O}_4\to F{e}_3{\left(P{O}_4\right)}_2+3H_2\uparrow$