If n (A-B) = 18, n (AuB) = 70 and n (AnB) = 25 then find n (B)

n (A-B) denotes elements which are in A but not in B

n (Au B) denotes elements in A and B

n (AnB) denotes elements that are common in A and B

Now I will add one more set

n (B-A) which denotes elements in B but not in A

So, n (AuB) = n (A-B) + n (B-A) + n (AnB)

70 = 18 + n (B-A) + 25

70 = 43 + n (B-A)

n (B-A) = 70-43

n (B-A) = 27

So, n (B) = n (B-A) + n (AnB)

= 27+25

= 52