Question

If P(A)= 0.3 and P(B|A)=0.9 what is P(A B)?

Answer 1

You seem to be missing a symbol, which I assume is intersection
`\cap`.

From the definition of conditional probability,


`\mathbb P(B|A)=(\mathbb P(B\cap A))/(\mathbb P(A))\implies0.9=(\mathbb P(B\cap A))/(0.3)\implies\mathbb P(B\cap A)=0.27`