with each number being the roll on the first and second die respectively. I think thats where they're getting the 5. Someone correct me if I'm wrong though.
5/36 x 5/36
to roll a sum of 6 the first time there are 5 possible way : (5 1) (1 5) (4 2) (2 4) (3 3) and same goes for the second roll
therefore its 5/36 x 5/36