Depending on the student and his situation: -Student in school: reminder of lessons and exercises, application of concrete cases - Out-of-school student: Detailed course of the chosen subject and exercises. - ability to concentrate: lessons between 1 and 2 hours. Depending on his ability to concentrate, the exercises could be done in the form of games in order to capture his attention. I always give examples of application so that the student understands the interest of studying these themes.