Basic strategy

#1
Hello everyone :)
I am doing a project about BlackJack, right now.
I have to account for what the probability is to win in 'BlackJack', if 3 decks are in play. I have found several Basic strategy calculator, but the problem is that these calculators do not shown the caculations.
It would be such an enormously help if someone could tell me the mathematical method to the caculations the basic strategy calculators do :)
 
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