Count back & use the relationship between addition and subtraction to subtract within 20. Warm up with a Mystery Math Mistake to find the error in DC's addition. Use ...

Addition & subtraction strategies to solve two-digit equations using an open number line. In this lesson, students go over using different addition and subtraction strategies to solve two-digit ...

Years ago, when her eighth-graders struggled with basic subtraction, teacher Rita Frenzel tried something different: She taught them chess. The math scores climbed, and so did a passion that would ...