A与B相互独立,P(AB)=P(A)P(B)
P(A∪B)=P(A)+P(B)-P(AB)=P(A)+P(B)-P(A)P(B)
所以0.5+P(B)-0.5P(B)=0.8,P(B)=0.6
P(ˉA∪ˉB)=P(ˉAB)=1-P(AB)=1-P(A)P(B)=1-0.5*0.6=0.7
P(A) + P(B) = P(A∪B)
P(B) = P(A∪B) - P(A) = 0.3
P(ˉA∪ˉB) = Pˉ(A交B) = 1-0.3*0.5 = 0.85
易知P(B)=0.6
原式=0.3
原式=1-P(AUB)=0.2