(1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99)
1 - Add up all the numbers from 1 to 49 inclusive and that is the value of your "x"
2 - Add up all the numbers from 51 to 99 inclusive and that is the value of your "y"
3 - Subtract "x" from "y" and that is the answer to your problem. Good luck.