Is n(A-B)=n(A)-n(B)?

For any two sets A and B prove that n(A-B)=n(A)-n(AnnB) .

If n(A-B)=10,n(AnnB)=5 and n(B-A)=20 ,then find n(B) and n(AuuB) .

Establish that: n(A uu B)=n(A)+n(B)-n(AnnB)

If A and B are two finite sets,then prove that n(A uu B)=n(A)+n(B)-n(AnnB)

If n(A uu B) = 50 , n(A) = 31 and n(B) = 23 , find n(A nn B) , n(A-B) and n(B-A)

If n(A')=15 , n(B)=5 , n(A nn B)=3 and n( uu ) = 30 then determine n(A) , n(A uu B) and n(A-B) where A and B are subset of a universal set U.

If A = { x : x = 4n + 1 , n is a natural number le 5 } and B = {3n : n is a natural number le 6 } then find (A-B) nn (B-A)

If n(A) = 30 , n(B') = 6 , n(A nn B) = 25 and n(B-A) = 37 , find n(B) , n(U) , n(A uu B) and n(A - B)

If n(A)=110,n(B)=300,n(A-B)=50,then find n(AUB).

If n(A)=80,n(B)=30,n(AuuB)=100 ,then find n[(A-B)uu(B-A)] .