Algebra is a foundational concept in the study of mathematics, and readers will delight in learning the principles of operations and algebraic thinking in a relatable and engaging way. Topics such as adding and subtracting within 20, using algebraic principles to solve equations and word problems, and understanding the relationship between addition and subtraction will give beginning math students a firm grasp on basic math concepts. Yolanda's family is having a yard sale, and by selling items from her home, she can demonstrate her ability to fluently subtract within ten. This volume meets CCSS Math Standard 1.OA.C.6.