Probability

There are $6 \times 6 \times 6 = 216$ possibilities. 

The only way to get a sum of 17 is to have a 6, 6, and 5, which can be done in $3! \div 2 = 3$ ways (divide by 2 because there are 2 6's)

So, the probability is ${3 \over 216} = \color{brown}\boxed{{1 \over 72}}$