start from here...How can P(B) = 0.5/0.3? That number is greater than 1!!so

P(A) + P(B) - P(A B) = P(A). P(B)

0.5 + P(B) - 0.8 = 0.5 P(B)

P(B) - 0.3 = 0.5 P(B)

P(B) = 0.5/0.3_{(Is this correct?)}

from my work can u please point out the mistake

P(B) - 0.3 = 0.5 P(B)

and solve for P(B) again.