Possible rolls with sums of 6 are (1,5); (2,4); (3,3); (4,2); (5,1).
Place these 5 possible results of 6 over the total number of possible outcomes for rolling 2 fair 6-sided dice to obtain 5/(6×6) or 5/36 equal to 0.1388888888889 or 13.8888888889% Probability.