Bunuel wrote:

Car X and Car Y were members of a cross-country race. If Car X and Car Y drove a total of 300 miles, how many miles did Car X drive?

(1) Car Y drove 3/4 as many miles as Car X did.

(2) Car X drove 11 percent of all miles driven in the race.

Total no. of miles drove by x and y = 300.

Question : How many miles car x drove ?

Statement 1:

Let care x drive x miles .

So y drive 3y/4 miles.

We can form an equation . Sufficient.

Statement 2:

Straight . 11% is given . it's the no. of miles driven by x. So, rest of the miles driven by x. Sufficient.

The best answer is D.

11% is given the all miles driven. Do we know that only x and y cars were in the race? Probably no. So we have no idea how much miles were driven by all participants, have we?