Answer:
all of U except 3 and 4, maybe (A ∩ B)' = {1, 2, 5, 6}
Step-by-step explanation:
Your problem statement tells you that in the intersection is 3 and 4, so ...
(A ∩ B)' is all of U except {3, 4}.
The only members of U listed here are {1, 2, 3, 4, 5, 6}. If that is all of U, then ...
(A ∩ B)' = {1, 2, 5, 6}