This system was in use pre Fidel Castro in Cuba. Basically a player bets one unit on the third column and another one unit bet on black. The reason for this combination of bets is that there are only 4 black numbers in the third column and 8 red. Therefore if one of the 8 red numbers from the third column comes up you will have won one unit. However if a number from the first or second column comes up there's a higher chance it will be a black number, for which you'll be break even if one of those's comes up.
Obviously if a red number from the first or second column does come up you will lose both bets. Of course if one of the 4 black numbers from the third column come up you win 2 bets.
The Cuban betting system is an interesting way to play especially to those players who like to keep betting amounts low and not increase there wagers. However mathematically its not a system which overcomes the house edge in the long run.
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