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Wanted outcomes are 3, 6, 9, 10, 11, 12.  
3 = 1+2, or 2+1,                ====>  so there are 2 ways to get the sum of 3.
6 = 1+5, 2+4, 3+3, 4+2, or 5+1  ====>  so there are 5 ways to get the sum of 6.
9 = 6+3, 5+4, 4+5, 3+6          ====>  so there are 4 ways to get the sum of 9.
10 = 6+4, 5+5, 4+6              ====>  so there are 3 ways to get the sum of 10.
11 = 6+5 and 5+6                ====>  so there are 2 ways to get the sum of 11.
12 = 1+1                        ====>  so there is  1 way  to get the sum of 12.
Thus you have  2 + 5 + 4 + 3 + 2 + 1 = 17 wanted cases of 36 possible outcomes.
The probability under the question is  
.