My Book of Subtraction - Kumon Workbooks This workbook will improve and expand on the skills acquired in My Book of SIMPLE SUBTRACTION. In this book, children will practice first how to subtract the numbers 1 through 9 and then they will reinforce this skill by learning how to subtract numbers 1 through 20. The purpose of this book is to prepare children for higher-level mathema... more »tics by improving their basic subtraction skills.« less