A large number of problems with mathematics in children are associated with a banal inability to quickly make simple arithmetic calculations. This notebook simulator will develop your child's ability to quickly, and most importantly, correct addition and subtraction in the mind in 21 days. The notebook was developed by Shamil Akhmadullin, the author of the bestselling books "Speed ​ ​ Reading for Children. How to teach a child to quickly read and understand what they read," "Memory development in children" and "How to teach a child a multiplication table in 3 days."