I think the question needs to be rephrased. Why would you need numbers 11-24?
Can you use a number twice?
Do you really mean if you have balls number 1-24 how may different combinations of 4 balls are there?
I partly agree dundurn, but I think you have to then divide that figure by 4x3 x2x1=24 to allow for the fact that the order of the balls doesn't matter. So, for example, you can get the numbers 5,8, 13 and 23 in 24 different ways ( 5, 18, 13, 24 and 5, 8, 24, 13 and ..etc)