How do you balance #CuCl_2 + Fe -> 2Cu + FeCl_2#?
I'd start by looking at what is the most complicated and unbalanced, as we can see there is only 1
So add a 2 in front of
But now Chlorine is unbalanced on the left side, as we have 4 on the right, so add a 2 in front of
Finally balance for iron as that is the only thing left by adding a 2:
And now it is balanced!