Answer:
0.953703703704
Explanation:
We have 6 × 6 × 6 = 216 possible results
You can make a table :
obtaining a sum of 18 in only one case : (6 ,6 ,6)
obtaining a sum of 17 in 3 cases : (5 ,6 ,6) ; (6 ,5 ,6) ; (6 ,6 ,5)
obtaining a sum of 16 in 6 cases : (5 ,5 ,6) ; (6 ,5 ,5) ; (5 ,6 ,5)
(4 ,6 ,6) ; (6 ,4 ,6) ; (6 ,6 ,4)