Bunuel wrote:

If xy = z, what is the value of x ?

(1) y = 2z

(2) z < -1

xy = z, x = ?

Statement 1:

y = 2z

Substituting, x*2z = z

If z is not equal to 0, we can cancel it and x would be equal to 1/2. But, if z is equal to 0, x could be anything (still satisfying the given information xy = z). Since we do not know if z is equal to 0 or not, this statement is insufficient.

Statement 2:

z < -1

So, xy < -1

This statement does not give any information about x and is therefore insufficient.

Combining statements 1 and 2,

z < -1

So z is not equal to 0. z can be divided on both sides of x*2z = z

Therefore, x = 1/2

Answer is

C.