Tricky math probability problem need help?

Question

Mary plays blackjack. She always doubles her money that she bets 90% of the time. She loses all the money she bets 10% of the time. She can bet once per day. She starts off with $1000. Assuming she wins her first bet, what percentage (X) of her winnings should she put in reserve in case she loses in order to maximize her total winnings over 365 days?

* If she loses, she bets her reserve, leaving (X)% of the reserve still in reserve.

Answer 1

"She always doubles her money that she bets 90% of the time" This makes your question impossible.  If she "always" does it, that is 100% of the time, not 90% of the time.  If she does it 90% of the time, that's not always.

Answer 2

100% cos it's stupid to bet at a casino - the chances of winning are very small unless you win the first time and then go home qand don't ever bet again.

so there........