One must divide the number of combinations producing the given result by the total number of possible combinations (for example, {49choose 6} = 13,983,816, as explained in the section above). The numerator equates to the number of ways one can select the winning numbers multiplied by the number of ways one can select the losing numbers.
For a score of n (for example, if 3 of your numbers match the 6 balls drawn, then n = 3), there are {6choose n} ways of selecting n winning numbers from the 6 winning numbers. This means that there are 6 - n losing numbers, which are chosen from the 43 losing numbers in {43choose 6-n} ways. The total number of combinations giving that result is, as stated above, the first number multiplied by the second. The expression is therefore {6choose n}{43choose 6-n}over {49choose 6}