Basic counting techniques are formed in the child in the first years of study. Therefore, it is very important to pay special attention to the development of these skills.Oral and written work with mathematical chains occupies an important place in acquiring calculation skills. Solving mathematical chains of examples will help the child work out and consolidate counting skills to automaticity, activate mental activity, develop memory, attention and speed of reaction, and prepare them to perform more complex calculations for multiplication and division. By solving a chain of examples from simple to more complex, students will work out the rules for the order of calculations in examples with and without brackets.The book includes topics: “Addition and subtraction within 5”, “Addition and subtraction within 10", "Addition and subtraction within 20 without brackets", "Addition and subtraction within 20 with brackets". In each version, examples are given for addition and subtraction with a different number of terms, with and without brackets.The book was prepared in accordance with the requirements of the Federal State Educational Standard for Primary Education. It can be used when working with any textbook included in the Federal List. The manual will be useful in mathematics lessons and for self-study at home.