Addition & Subtraction. Free Printable worksheets & Quizzes. Fact ... Teach by using fact families! Memorize one, get three free. 2+8=10 therefore 8+2=10, 10-2=8, 10-8=2. You will also find mixed addition and subtraction worksheets, double-digit, triple digit addition and subtraction worksheets with and without regrouping. Add and subtract within 20. CCSS.Math.Content.1.OA.B.3