Edit:
Use this fact: .
&
If P(A) = 0.2, P(A|B) = 0.3, P(A u B) = 0.4. Find P(B).
Reminding you that:
P(A n B) = P(A) + P(B) - P(A u B)
P(A u B) = P(A) + P(B) - P(A n B)
& that P(A|B) = P(A n B) / P(B)
I think I've got to use simultaneous equations... I just can't figure out where.
Any help? Please show working.
Thanks