9514 1404 393
Answer:
(x, y, z, w) = (14, 6, 11, 8)
Explanation:
It usually works well to work outward from the region with the most overlaps. Here, that is y.
y = A∩B = 6
x + y = A = 20 ⇒ x = 20 -6 = 14
x + y + z = A∪B = 31 ⇒ z = 31 -20 = 11
w + x + z = A'∪B' = 33 ⇒ w = 33 -14 -11 = 8
In summary, (x, y, z, w) = (14, 6, 11, 8).