For the answer to the question above, 1.18 x 3 = 3.55.
First, you need to find the ratio of F to F in each compound. It is the law of multiple proportions stating that the masses of one element which combine with a fixed mass of the second element are in a ratio of whole numbers. In this case, F would be the "one element" and S would be the "fixed mass", the ratio of F6 to Fx = 3:1
therefore x would be 2 since there is less F in SFx and the ratio is 3:1. divide 6 by 3 and you get 2.