设A,B是两个事件,已知p(A)=0.4,P(B)=0.7,P(AUB)=0.8,试求P(A-B).

P(A∪B)=P(A)+P(B)-P(A∩B)
0.8=0.4+0.7-P(A∩B)
∴ P(A∩B)= 0.3
∴ P(A-B)=P(A)-P(A∩B)=0.4-0.3=0.1