While there isn't a single narrative "story" associated with it, these materials are widely used study aids in Russia designed to help students check their homework or understand complex topics like:
Calculating area and volume, and basic data organization. gdz po matematike 6klass zubareva mordkovich
Since GDZ content is usually hosted on specific educational portals, you can often find them by searching for the specific exercise number alongside the authors' names. Grade 6 B.E.S.T. Instructional Guide for Mathematics While there isn't a single narrative "story" associated
Introduction to variables, solving simple equations, and identifying numerical patterns. solving simple equations
Operations including addition, subtraction, multiplication, and division.
Understanding negative numbers, absolute value, and their placement on a coordinate plane.