[INST] Three fair, standard six-sided dice are rolled. What is the probability that the sum of the numbers on the top faces is 18? Express your answer as a common fraction./n [/INST]  ###Response: The probability of rolling three fair, standard six-sided dice and getting a sum of 18 is 1/216. This is because the only way to get a sum of 18 with three dice is if each die shows a 6, which has a probability of 1/6. So the probability of getting three 6's in a row is (1/6)^3 = 1/216.