The Mordkovich system is famous for its "functions-first" approach. Unlike traditional curricula that start with abstract numbers, this book introduces the concept of a and functions early on to give students a practical framework for solving problems.
The textbook is excellent for developing logical rigor. If you are using GDZ with it: algebra 7 klass a.g.mordkovich n.p.nikolaev gdz
Pay attention to how they simplify expressions before solving—this is the "trick" to the Nikolaev advanced problems. The Mordkovich system is famous for its "functions-first"