Possible prime sums are 2,3,5,7, and 11

number of ways to get 2 = 1

numbr of ways to get 3 = 2

number of ways to get 5 = 4

number of ways to get 7 = 6

number of ways to get 11 = 2

total = 15

prob of that happening = 15/36 = 5/12

so prob of that NOT happening = 1-5/12 = 7/12

odds in favour of a sum which is prime = (5/12) : (7/12)

= 5 : 7