A Pairs of fair dice is tossed. What is the probability of not getting a sum 7 or 8?

A Pairs of fair dice is tossed. What is the probability of not getting a sum 7 or 8?

Not a 7 or 8 means 2 - 6 or 9 - 12
Using our 2-dice calculator, P(2 - 6) = 5/12
Using our 2-dice calculator, P(9 - 12) = 5/18

Since the sum could be either of these, we add probabilities:
P(Not a 7 or 8) = P(2 - 6) + P(9 - 12)
P(Not a 7 or 8) = 5/12 + 5/18
P(Not a 7 or 8) = 25/36