ok there are 3 cups, one filled with poison, the other antidote, and a third one negates the antidote, you have to drink 2, what is your chance of survival?
options:
1.-Poison + antidote (survive)
2.-Poison + ne.antidote (die)
3.-antidote + ne.antidote(survive)
So 0.66 is the probability.