Explanation:
any particular result with 2 dice has a probability of
1/6 × 1/6 = 1/36
a 3 on one die or both simply means at least one 3.
so, if all the 36 different outcomes we are looking at
3 1
3 2
3 3
3 4
3 5
3 6
1 3
2 3
4 3
5 3
6 3
the 3 3 combination can be counted only once !
so, we have 11 desired outcomes out of the possible 36.
so, the probability of getting at least one 3 is
11/36
the sum of at least 10 means the corresponding cases
4 6
5 5
5 6
6 4
6 5
6 6
in this case we don't need to turn this around, because it would be exactly the same outcomes again, and we don't want to count them twice.
so, we have 6 desired outcomes of the 36.
the probability of that is
6/36 = 1/6