Math Help - Combinatorics and subsets #1

1. Combinatorics and subsets #1

1) {1,2,3, .., 100} set of 101 randomly selected likely to be the sum of two elements, what is the value of a subset of numbers?

2) {1,2,3, .., 50} a set of randomly selected a subset of the many 5-element in this set of elements likely to be what is the value of the total 25?