Since, much is not given here I assume that the full amount of the players is doubled.

After the end of three rounds, amounts of the players were(in dollars)

24,24,24

Let us say that the third player lost the third round. Hence, the amount the players possess at the beginning of third round(and at the end of second round)

12,12,48

Let us say that the second player lost the second round. Hence, the amount the players possess at the beginning of second round(and at the end of first round)

6,42,24

Let us say that the first player lost the first round. Hence, the amount the players possess at the beginning of first round(and at the end of first round)

39,21,12