There are two situations. First, if A wins the next game, then the money belongs to A, and the probability is 1/2.

Second: Next sentence, A loses, and the probability is. 1/2. Then each of them won four games.

So if A wants to win all the money, the next sentence must win, and the probability is 1/2.

So the probability that A loses one game first and then wins another game is1/2x1/2 =1/4.

So the money won by A may all be1/2+1/2×1/2 = 3/4.

I still hope you can adopt it ~