Question 1078969
P (a or b)=p(a)+p(b)-p(both)
73/100=55/100+p(b)-(.55*P(b))
9/50=0.45 p(b)=0.18
p(b)=2/5 or .40.
The important part here is that they are said to be independent.  That gives the joint probability part.  If they were mutually exclusive, 9/50 would work.