In developing this research, we got supported by the use of different strategies for solving problems, based on authors such as Cavalcanti (2001), Krulik and Reys (1997) and Pozo (1998). We highlighted as research issue to investigate "What are the different strategies that students use to solve problems and how these interfere in this process?". This research is predominantly qualitative and is characterised in a case study. Initially, 158 students solved a selection of eight problems. The resolutions were analysed under the perspective of different strategies that could be used in solving mathematical problems. We have detected the predominance of formal calculation with a low rate of success in the resolution of most problems. From this result we are developing actions that aim to improve the teaching and the learning of problem solving, exploring different strategies. We are conducting an ongoing education with teachers and experiencing a pedagogical intervention with students.