card(A ∪ B) = 10
card(A - B) = 3
card(B - A) = 2
card(A) = card(A ∪ B) - card(B - A)
= 10 - 2 = 8
card(B) = card(A ∪ B) - card(A - B)
= 10 - 3 = 7
Alte formule:
card(A ∪ B) = card(A) + card(B) - card(A ∩ B)
card(A - B) = card(A) - card(A ∩ B)
card(B - A) = card(B) - card(A ∩ B)