First, let's write the givens in the form of a chemical equation:
3A + B ...................> 4X + 2Y
Now we find that this equation implies the following:
For every 4X and 2Y formation, 3A and 1B must disappear (react).
Comparing this implication to the above choices, we find that the right answer is: The rate of formation of X is four times the rate of disappearance of B.