2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/66986A set A of integers is said to be sum-free if there are no solutions to the equation x + y = z with x,y and z all in A. Answering a question of Cameron and Erdos, we show that the number of sum-free subsets of {1,...,N} is O(2^(N/2)).11 pages, to appear in Bull. London Math. SocNumber TheoryCombinatorics11B75text