Which is the next logical step in balancing the given equation? cs2(1)+cl2(g) ccl4(1) s2cl2(1)

Reaction of current interest is: 

CS2(l)       +          Cl2(g)          →       CCl4(l)     +     S2Cl2(l)

While balancing the chemical reaction, care must be taken that number of atoms of reactant side is equal to number of reactant on product side. 

In present case, There is 1 'C' atom of both reactant and product side
There are 2 'S' atoms on both reactant and product side.
However, there are 2 Cl atoms of reactant side, but 6 Cl atoms on product side.
Hence multiplying Cl2 by 3, would equal the number of Cl atoms on both the sides.

Thus, the balanced reaction is
CS2(l)       +         3 Cl2(g)          →       CCl4(l)     +     S2Cl2(l)