damn it stupid thing messed up. gotta retype it now...
ok i believe this is how it goes.
This is how the reaction rate works.
aA + bB -> cC + dD
the reaction rate for this would be: rate = k [A]^a ^b
so for the example you gave where concentrations are doubled for both: rate = k[W]^2 [X]^2
if you increase ONE of the reactants by two, the rate increases by a factor of 4 (2^2). If you increase BOTH of the reactants by two like the problem states, the rate would increase by a factor of 16 (2^2) * (2^2)
hope that helps =)