There are 36 possible results of throwing two dice. Of these there are 5 adding up to 6: (1,5), (2,4), (3,3), (4,2), 5,1); and two adding up to 11: (5,6), (6,5). Therefore the probabilities are 5/36 and 2/36=1/18 for 6 and 11 respectively. The probability of either one or the other is 7/36.