Answer:
a+b = 12
Step-by-step explanation:
There are 36 possible outcomes for rolling two dice. Let A be the number rolled by Abed and D be the number rolled by Dawn. The sample space, in the format [A,D], of all of the possibilities in which Dawn's number is larger is:
[5,6]
[4,5] [4,6]
[3.4] [3,5] [3.6]
[2,3] [2.4] [2,5] [2.6]
[1,2] [1,3] [1.4] [1,5] [1.6]
There are 15 ways out of 36 possible ways of Dawn getting the higher number. In the simplest form:
