The present study shows how students, eleven years old, solve problems in mathematics when they work together in groups. The main question raised is about the difficulties students experience in finding the relationship between mathematics and everyday discourse and vice versa. Two empirical studies about students' problemsolving in mathematics divided into three different articles are presented in this study. One is about how students discuss, while they are trying to solve what the area of the triangle is. The other study is about how different solutions in problemsolving have various meanings. The main finding ofthis work concems communication. Depending on the social contexts, different kinds oflanguages are developed in. When children are in their everyday contexts, they use one kind oflanguage, that is they use everyday concepts. In school, children have to leam the language ofmathematics. Leaming mathematics is about getting students to use the language of mathematics to mediate events and phenomens in the world around. One can describe learning as assimilating communicative and technical tools. Which are used as mediating tools in social practices. Another main finding of this study is to show how a teacher can get students attentive to how to change between different types of discourse and how to use special conc~pts for a special context. The most important aspect is that a teacher has pedagogical conversations with students on how to move between different communicative contexts. Often, students have difficulties in understanding in which communicative context they are involved.