Question

(The set of all such that)
A={n in Z| 2 divides n}
B={n in Z| 3 divides n}

Both are contained in the universal set
U=Z

a/ What is A union B?
b/ What is the complement of A?

Answer 1

a/ Sorry, it was what's A intersection B?

Answer 2

A={n ∈ Z| 2 divides n}
B={n ∈ Z| 3 divides n}

A∩B
={n in Z| 2|n and 3|n}
={n in Z| 6|n}
That is
A∩B is the set of all integers divisible by 6.

A'={n in Z| 2∤n}
= all odd integers.