Simply double your bet every time you lose and when you win you will be ahead. For this to work there would have to be a lot of tables around with a wide range of possible betting.
Your chances of losing 20 in a row is practically 0. You would need a bankrole of like 2million though.
Your chances of losing 20 in a row is practically 0. You would need a bankrole of like 2million though.