A is the set of all even natural numbers, and B is the set of all odd natural numbers. Describe a universal set for A and B. Also, with respect to this universal set, give a relationship between A and B.

Now, what happens when I take all the even natural numbers, such as 2,4,6,8,...
and combine them with the set of all odd natural numbers, which would be 1,3,5,7,... ?