2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/150192A new, simple method to approach enumerative questions about rational curves on rational surfaces is described. Applications include a short proof of Kontsevich's formula for plane curves and a the solution of the analogous problem for the Hirzebruch surface F_3.25 pages, Tex type: Plain, figures are not included in the package, for a copy with pictures write to bwatson@abel.harvard.eduAlgebraic Geometrytext