Which of the following coefficients correctly balances the following chemical?

You have 3 Cl on the right so you need 3 HCl on the left.
Fe + 3HCl --> __H2 + FeCl3

Now you need to double the numbers to get H2.

2Fe + 6HCl --> 3H2 + 2FeCl3

Now you have 2 Fe left and right, 6 H left and right, and 3 Cl left and right.