Answer
CH4 + 4Cl2 -> CCl4 + 4HCl
Work Step by Step
CH4 + Cl2 -> CCl4 + HCl
First we balance the C since it appears only once and it seems simple. There is 1 C on the left and 1 on the right so it is done.
Next we balance the Hs since it appears only once on each side. There are 4 on the left and 1 on the right so we need to multiply the HCl term by 4
CH4 + Cl2 -> CCl4 + 4HCl
Now we balance the Cls. We have 2 on the left and 8 on the right so we multiply the Cl2 by 4 to give 8
CH4 + 4Cl2 -> CCl4 + 4HCl