Question 1181088
P(A)=7/20
P(A∪B)=191/400
P(A∩B)=49/400 
P(B)=?
<pre>
 P(A∪B)=P(A)+P(B)-P(A∩B)
191/400=7/20+P(B)-49/400
Multiply every term on both sides by 400
    191=140+400P(B)-49
    191=91+400P(B)
    100=400P(B)
100/400=P(B)
    1/4=P(B)

Edwin</pre>