If n(A)=14, n(B)=51, and n(A∩B)=12, then what is n(A∪B)?

Answer 1

n(A U B) = n(A) + n(B) - n(A∩B) = 53

Answer 2

Then there is 2 in A only

And

39 in B only

So

2+12+39=53