The problem is as follows:

> 
> Let X be the winnings of a gambler. Let $p(i)=P(X=i)$ and suppose that   
> 
>  $p(0)=1/3;\\ p(1)=p(-1)=13/55;\\p(2)=p(-2)=1/11;\\p(3)=p(-3)=1/165$.
>    
> 
>  Compute the conditional probability that the gambler wins $i$, $i=1,2,3$ given that he wins a positive amount. 
> 
> 
> 

I am not looking for a solution, but just be pointed in the right direction to begin solving this question. 

I don't think this has been posted before, at least I was unable to find this question. If it has, I apologise.