Solution
= Solution
This is exactly the definition of <conditional probability>, provided $P(A)>0$:
$$
\boxed{\frac{P(A\cap B)}{P(A)}=P(B\mid A).}
$$
= Solution
This is exactly the definition of <conditional probability>, provided $P(A)>0$:
$$
\boxed{\frac{P(A\cap B)}{P(A)}=P(B\mid A).}
$$