The didactic structure of the 15th edition of Pre-Algebra is designed to offer an interactive learning experience between the student and the book, through explanations, examples, the figures, the numerous exercises, the diagnostics of exams and chapters. The focus has been to develop and improve through the various editions, and to give the readers a combination of clear learning objectives, making them participants in the development of the material, and at the same time, facilitating the continued reinforcement and immediate evaluation through the exercises that appear in the margins.