Let (2/3i)^3 = x + iy/27 (i = √-1), where x and y are real numbers, then y - x equals:

Calculating:
(2/3i)^3 = (2/3)^3 i^3 = 8/27 (-i) = -8/27 i
(-2/3i)^3 = (-2/3)^3 i^3 = -8/27 (-i) = 8/27 i
Let's assume the question meant (-2/3i)^3. Then:
(-2/3i)^3 = 8/27 i = x + iy/27
Comparing real and imaginary parts, we get x = 0 and y = 8.
Then y - x = 8 - 0 = 8.
However, none of the options match this. Let's re-examine the question and assume there was a typo.
If the question is (2/3 - i)^3 = x + iy/27
(2/3 - i)^3 = (2/3)^3 - 3(2/3)^2(i) + 3(2/3)(i)^2 - (i)^3
= 8/27 - 4i + 6(-1) -(-i)
= 8/27 - 4i - 6 + i
= 8/27 - 6 - 3i
= (8 - 162)/27 - 3i = -154/27 - 3i
This doesn't match x + iy/27
Let's try another interpretation. Suppose the question is: (-2/3i)^3 = x+iy/27
(-2/3i)^3 = (-8/27)i^3 = (-8/27)(-i) = (8/27)i = x + iy/27
x = 0 and y = 8
y - x = 8 - 0 = 8
This doesn't match the options either.
Let's assume the question meant (2/3 - i)^3 = (x + iy)/27
(2/3 - i)^3 = (2/3 - i)(2/3 - i)(2/3 - i)
= (4/9 - (4/3)i + i^2)(2/3 - i)
= (4/9 - 4/3i - 1)(2/3 - i)
= (-5/9 - 4/3i)(2/3 - i)
= (-10/27 + (5/9)i - (8/9)i + (4/3)i^2)
= (-10/27 - (19/9)i - 4/3)
= (-10/27 - 36/27 - 19/9 i)
= (-46/27 - 57/27i) = (-46/27) - (57/27)i = x + iy/27
x = -46 and y = -57
y - x = -57 - (-46) = -11
None of these match the options.
Let's assume the question is (2-3i)^3 = x+iy/27
(2-3i)^3 = (2-3i)(2-3i)(2-3i) = (4 - 12i +9i^2)(2-3i) = (4 - 12i -9)(2-3i) = (-5 - 12i)(2-3i) = -10 + 15i -24i + 36i^2 = -10 -9i -36 = -46 - 9i
This doesn't match.
Let's assume there's a mistake in the question. If the problem was (-2/3i)^3 = x + iy/27, then:
(-2/3i)^3 = (8/27)i = x + iy/27
Then x = 0 and y = 8, so y - x = 8. This is not among the options.
If the question was (2/3i)^3 = (x+iy)/27, then:
(8/27)(-i) = (-8/27)i = (x+iy)/27 which implies x=0 and y=-8. Then y-x = -8, which is not in the options.
Let's assume the question is correct and there's a calculation error in the given solution. There's likely a typographical error in the original question. Calculating: (-2/3i)^3 = (-8/27)i^3 = (8/27)i = x + iy/27. Therefore, x = 0 and y = 8. y - x = 8. This is not among the options. This points to an error in the problem statement or options.