Question

If A and B are two sets such that n(A) = 115, n(B) = 326, $n(A-B)$ = 47, then writen $(A\cup B)$.

Answer 1

$n(A-B)=n\left(A\right)-n(A\cap B)$

$n(A\cap B)=n\left(A\right)-n(A-B)$

$n(A\cup B)=n\left(A\right)+n\left(B\right)-n(A\cap B)$

$n(A\cup B)=n\left(A\right)+n\left(B\right)-\left[n\right(A)-n(A-B)$]

= $n\left(A\right)+n\left(B\right)-n\left(A\right)+n(A-B)$

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

= 326+47

373