Formulae for Probability
Works for All Cases:

P(A∪B)=P(A)+P(B)P(A∩B)

P(AB)=

P(A’)=1P(A)
For Mutually Exclusive Events Only:

P(A∩B)=0
For Independent Events Only:

P(A∩B)=P(A) P(B)

P(AB)=P(A)

P(BA)=P(B)

P(A’∩B)=P(A’) P(B)

P(A∩B’)=P(A) P(B’)

P(A’∩B’)=P(A’) P(B’)