p(A)* A = { & lt； & lta，a & gt，a & gt，& lt& lta，b & gt，a & gt，& lt& ltb，a & gt，a & gt，& lt& ltb，b & gt，a & gt，& lt& lta，a & gt，b & gt，& lt& lta，b & gt，b & gt，& lt& ltb，a & gt，b & gt，& lt& ltb，b & gt，b & gt}
For any event P(AB)=P(A)-P(A non-B) P(AB)=P(B)-P (non-AB)?
If A and B are independent of each other, P(AB)=P(A)P(B)
When P(A) >; 0 P(AB)=P(A)P(B|A)
When P(B)>0 P(AB)=P(B)P(A|B)
Expand data p (a/b) = P(AB)/p (b) p (b/a) = p (ab)/p (a) The key is to find p (ab).
If A and B are independent of each other, P(AB)=P(A)*P(B)
If it is not independent, if another P(A+B) is known, it can be found by P(A+B)=P(A)+P(B)-P(AB).