The first cube can land in any one of 6 ways.
The second cube can land in any one of 6 ways.
Total number of ways that 2 dice can land = (6 x 6) = 36 ways.
For any of these ways, the sum of the numbers rolled is 9 :
3, 6
4, 5
5, 4
6, 3
There are 4 ways to roll a 9, out of a total of 36 ways that
the dice can land. So the probability of rolling a 9 is
4 / 36 = 1 / 9 = 11-1/9 percent