Question

If n (A ∪B) = 25 , n(A) = 12 , n(A -B) = 8 , then write the number of elements in n(A ՈB)and n(B –A).

Answer 1

Answer:

n(A∪B ) = 25

n(A) = 12

n(A - B) = 8

n(A∩B) = n(A) - n(A - B) ∵n(A) = n(A - B) + n(A∩B)

you can also check by drawing venn diagram

n(A∩B) = 12 - 8

= 4

n(B - A) = n(A∪B) - n(A)

= 25 - 12

= 13

Answer 2

Answer:

n (AUB) = n (A)+n (B)-n (AnB)

25=12+n (B)-4

25=8+n (B)

17=n (B)

n (B-A)=17-4=13