X: Mr. A selected wining horse X : Mr. A did not select wining horse Mr. A selected two horses, now probability of not wining the first horse which Mr. A choses= ‌
4
5
And probability of not wining the second horse also which Mr. A choses =‌
3
4
(Here Mr. A out of remaining 4 horses choses one horse among 3 horses which did not win) ∴P(X)=‌