Question

if n(AUB) = 51, n(A) = 20, n(B) = 44 then find the value of n(A∧B)

Answer 1

i think n(A∧B) = 13 but not exactly

Answer 2

there is a formula for it
n(AUB) = n(A)+n(B)-n(A∧B)
now just substitute
51=20+44-n(A∧B)
n(A∧B)=15