Answer with explanation:
There are two sets A and B having n and m elements.
N(A)=n
N(B)=m
→N(A ∪ B)=Common as well as non common elements of Set A and Set B.
So, N(A∪B) ≤ m +n
→N(A∩B)=Common elements of Both A and B
N(A∩B)<n
N(A∩B)<m
→ N(A∩B)=m or n or m-n or n-m,depending on m>n , or , n> m or if , m=n.
→N (A-B)=Common elements of set A is excluded from set B and remaining elements are written
=n, if there is no common element
= n-m, if there is some common element.