Question 577857

P(A) = 0.2, P(B) = 0.5, P(A\B) = 0.3:

P(A\B) = P(A and B) P(B)
  0.3  = P(A and B) 0.5
  0.15   P(A and B)
P(A and B) = 0.15


B.   P(A or B) = P(A) + P(B) - P(A and B)
                 0.2  + 0.5  -    0.15
                   0.70      -    0.15 = 0.55