The Turf Puzzle

To show how little the patrons of the turf know about the theory of odds as practiced at the race track, let readers seek a solution to the following elementary problem:
If the odds are 7 to 3 against Apple Pie and 6 to 5 against Bumble Bee, what should be the odds against the famous running horse Cucumber?
-Sam Loyd, Cyclopedia of Puzzles, 1914