Answer:
25/216
Explanation:
Basically, if the numbers on two of the dice are decided, then there is only one value of the third die that is possible. So you have to find only those combinations of two dice that yield a sum of 6 or above. e.g. If the value on the 1st die is 1, then you have two possible outcomes - 5 or 6 on the 2nd die. Similarly, for a value of 2 on the first die, you have 3 possible outcomes (4, 5, 6) and so on... However, if you get a value of 6 on the first die, then you can have only 5 possible outcomes.
The total number of outcomes comes out to be (2 + 3 + 4 + 5 + 6 + 5) = 25.
Probability is 25/216!