This Work of Professional Assessment has the purpose of improving the resolution of problems of the students of the 1st grade of Secondary Education of the I.E. Nº 64736 “Flor de Selva” of the Flor de Selva village, of the Pampa Hermosa district, of the Ucayali province, of the Loreto Region, by means of the use of Realistic Mathematics Education. The problem observed in the students of the 1st grade of Secondary Education, in the development of problem solving, was the following: Most students are unable to pose problems based on a situation or a given fractional numerical expression. They present deficiencies in the process of expressing understanding of numerical concepts, operations and properties, and units of measurement; they have difficulties in selecting a variety of procedures such as mental calculation, estimation, and measurement; they fail to elaborate statements about ...