If a dice is rolled 3 times, then the number of possible outcomes are 63 = 216
The possibilities of getting sum of 9 are {(3,3,3), (2,4,3), (3,4,2), (2,3,4), (4,2,3), (1,4,4), (4,1,4), (4,4,1), (2,5,3), (2,3,5), (5,2,3), (5,3,2), (3,2,5), . . }
Probability of getting the sum of 9 for 3 dice = 25/216.