The purpose of this study is to describe the process of student interaction in solving problems through cooperative learning. The subject of this research are 7 th grade students of a junior high school in Malang, Indonesia. Data were collected by recording directly when learning takes place especially when pairing or forming small groups. This interaction is built with heterogeneous student skills. The results showed that the interaction that occurs in students provides an understanding of the concept of opportunity. Consequently, the students solved the problem correctly. This interaction is known as productive interaction.