The aim of the research presented in this paper is to contribute to our knowledge about problem solving in mathematics. My purpose in this paper is to compare, from this point of view, two very different institutions in the French tertiary education system, with the intention to interpret the chronic inequality of performance in problem solving between populations of mathematics students coming from these institutions. Problem solving knowledge and skills are not an explicit objective of teaching and their development depends largely on the student's private mathematical activity. This hypothesis is the reason why the inquiry aims at comparing mathematics students' ways of working as they study in both institutions. The results of the research are interpreted, on the institutional level, as effects of differences between the two teaching systems.