Question

n(A-B)=10
n(B-A)=14
n(AпB)=6
FIND n(AUB)

Answer 1

n(AuB=n(a-b)+n(b-0)-n(anb)
N(aub)=10+14+6=30

Answer 2

so given 

n(A-B) = 10
n(A+B) = 14
n(AпB) = 6

so we have  n(A-B) + n(A+B) + n(AпB) = n(AUB)
⇒n(AUB) = 14 + 10 + 6 = 30 ANSWER