Answer:
A ∪ B = [3, 9)
Explanation:
Set X is 3, and all number greater than 3 up, but not including, 5.
Set Y is all numbers from 4 to 9, but not including 4 or 9.
The union of the sets is all numbers from 3 up to 9, including 3 but not including 9.
A ∪ B = [3, 9)