2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/101084Let A be a subset of a finite abelian group G. We say that A is sum-free if there is no solution of the equation x + y = z, with x, y, z belonging to the set A. In this paper we shall characterise the largest possible sum-free subsets of G in case the order of G is only divisible by primes which are congruent to 1 modulo 3. The result is based on a recent result of Ben Green and Imre Ruzsa.22 pages, no figures, some corrections made, expanded exposition, a minor remars on k-l free sets added, bibliography updatedNumber Theory11p70text