The study reported in this book focused on teachers task practices in relation to teachers knowledge. The current mathematics curricula around the globe call for learning experiences, particularly tasks that support learners active participation in developing mathematical ideas in the classroom. Tasks differ in qualities and possibilities for learners participation and thus, teachers regularly make choices in terms of tasks for learners to work on. The criteria that inform teachers choices of tasks, how teachers and students work with the selected tasks in class, how teacher knowledge is...