This paper describes the design, implementation, and results of a training action with prospective primary education teachers, focusing on the creation of problems involving proportional and algebraic reasoning. Prospective teachers must solve a proportionality problem using both arithmetic and algebraic procedures, and then vary it to motivate proto-algebraic activity. Results show that participants successfully solved the task and created significant problems, which mostly motivated the expected algebraic activities. However, it can be observed that aspects of proportional reasoning or representations typical of proto-algebraic levels were not considered, which could have generated greater richness in the variety of problems created.