Solve the missing addend, determine whether the addition and subtraction equations are true or false, and master addition and subtraction within 20 with these 1st grade math worksheets. These printable worksheets can be assigned for subs, early finishers, or homework. Reasons why you need this product:It contains B&W worksheets you can print and hand to your students. There are no color copies included. The answer key is provided.The skills covered are Common Core aligned (1.OA.B.3, 1.OA.B.4, 1.