To find the value of x, we can use the given information.
We are given that x = y = 2z and xyz = 256.
Since x = y, we can substitute x with y in the second equation:
xy * z = 256
(x * x) * z = 256
x^2 * z = 256
Now, we know that x = 2z, so we can substitute x in terms of z:
(2z)^2 * z = 256
4z^2 * z = 256
4z^3 = 256
To solve for z, we can divide both sides of the equation by 4:
z^3 = 64
Taking the cube root of both sides gives us:
z = 4
Now that we know the value of z, we can substitute it back into the equation x = y = 2z:
x = y = 2 * 4
x = y = 8
Therefore, the value of x is 8.
The answer is: C. 8