Math Mammoth Add & Subtract 2-AMath Mammoth Add & Subtract 2 A deals with two main themes: strategies for adding and subtracting within 0 20; such as adding just one more, a trick with nine and eight, and subtracting using addition; memorizing the basic addition and subtraction facts of single digit numbers with an answer between 10 and 18. While focusing on addition and subtraction techniques, the lessons also include many word problems. The goal is to memorize the facts, or at