Final answer:
The set X = {100, 500} has 3 proper subsets, which are calculated using the formula 2^n - 1, with n being the number of elements in the set.
Step-by-step explanation:
The question is asking how many proper subsets the set X = {100, 500} has. A proper subset is a subset of a set that does not contain all the elements of the original set. To find the number of proper subsets, you can calculate 2^n - 1, where n is the number of elements in the original set. In this case, set X has 2 elements, so the calculation would be 2^2 - 1 = 3. Therefore, the set X has 3 proper subsets, which are: {100}, {500}, and the empty set {}.