$$ \begin{aligned} P(B-A)&=P(B)-P(AB) \ P(A\cup B)&=P(A)+P(B)-P(AB) \ P(A\cup B \cup C) &=P(A)+P(B)+P(C) \ &-P(AB)-P(AC)-P(BC) \ &+P(ABC) \end{aligned} $$
$$ \begin{aligned} P(AB)&=P(B|A)P(A) \ P(ABC)&=P(BC)P(A|BC) \ &=P(B)P(C|B)P(A|BC) \end{aligned} $$