Ключевые слова: abacus, add, addition, arithmetic, baby, boy, calculation, caucasian, child, count, decision, education, elementary, exam, example, exercise, grade, home, homework, indoors, kid, knowledge, learn, lesson, logic, math, mathematics, numbers, prepare, preschool, preschooler, problems, remember, room, school, schoolbook, science, simple, skill, solve, student, study, subtraction, task, test, textbook, think, workbook, write,