2Al+6HCl ----> 2AlCl3+3H2
Explanation :
First balance no of chlorine as
Al+3HCl---->AlCl3+H2
Now no of H2 is balanced by multiplying HCl with 2 and H2 with 3 as
Al+6HCl--->AlCl3+3H2
Now AlCl3 is balanced by doubling as
Al+6HCl--->2AlCl3+3H2
finally Al is balanced and net balanced equation is
2Al+6HCl -----> 2AlCl3+3H2