Question

if n(U)=35,n(A')=10,n(B')=15 and n(A n B)=15 then find n(A u B)

Answer 1

n(A') = 10
n(U) - n(A) = 10
n(A) = 25

n(B') = 15
n(U) - n(B) = 15
n(B) = 20

n(A∪B) + n(A∩B) = n(A) + n(B)
n(A∪B) = 30

Answer 2

It is 30........................