In this lesson, students begin working with equivalent expressions that involve negative numbers. They apply what they have learned about rewriting subtraction as adding the opposite. This enables students to apply properties of addition to generate equivalent expressions. For example, can be rewritten as and then rearranged as using the commutative property of addition. Then students use a similar strategy to make sense of the distributive property of multiplication over subtraction. As students rewrite an expression in different ways, they make use of structure (MP7).