This article reports from a study of mathematics classrooms. It is about the interaction that emerges when students are solving tasks from the textbook and the teacher gives individual assistance. The interest lies in the task and the way in which the teacher-student interaction is influenced by the textbook. An analysis of classroom episodes reveals control features of the textbook and shows that a textbook task, in an interrelationship with a teacher, can cause ambiguity as well as generate mathematical discussions.