The task is to compare x and z, so start by expressing one in terms of the other:

$$\frac{\text{1}}{\text{3}}x-\frac{3}{4}y=\frac{\text{1}}{\text{6}}z$$

4x – 9y = 2z
4x = 2z + 9y

Set up an implied inequality to compare the two quantities. In an implied inequality, you can add or subtract the same amount from both sides without changing the relative values (i.e. which one is greater). Likewise, you can multiply or divide by a positive number without changing the relative values. Do so to simplify:

(For that second-to-last step, remember that $y<\frac{\text{1}}{\text{5}}z$ is a given constraint. We have substituted for y according to this inequality, just in words and decimal form.)

The correct answer is B.