Let (p,q) denote a typical throw in which first number is thrown by A and second by B.
Then A can throw a higher number than B in the following 15 ways:
(2,1),(3,2),(3,1),(4,3),(4,2),(4,1),(5,4),
(5,3),(5,2),(5,1),(6,5),(6,4),(6,3),(6,2),(6,1),
Hence the number of ways in which A's throw is greater than B's =36−15=21
Hence odds in favor of A not throwing a number greater than B are as 21:15, i.e. 7:5.