From the position of the importance of the formation of universal educational actions through the material of meaningful lines (their fragments), as well as the basic didactic units of the school mathematics course, the article defines and describes the procedure for the «reversibility» of students' activities in the chain «subject material» - «universal educational actions». Educational tasks, cognitive tasks, and educational-cognitive tasks for subject tasks are offered as a means of realizing «reversibility». The reversibility methodology is illustrated for specific cognitive universal educational actions (search and selection of necessary information, independent selection of a cognitive goal, structuring of knowledge, choice of methods for solving problems depending on specific conditions, reflection of methods and conditions of action, monitoring of the activity process, analysis, comparison, classification, the establishment of causal relationships, the creation of algorithms) on a specific mathematical content - tasks for the construction of sections.