# Lesson 7

Why Is That Okay?

These materials, when encountered before Algebra 1, Unit 2, Lesson 7 support success in that lesson.

### Lesson Narrative

The mathematical purpose of this lesson is to review algebraic moves that preserve equivalence of expressions, specifically the distributive, commutative, and associative properties. The work of this lesson connects to previous work done in grade 7, when students used properties of operations to generate equivalent expressions. This lesson prepares students for the work in the associated Algebra 1 lesson because they will recognize equivalent equations and explain why they share the same solution. Students have an opportunity to look for and make use of structure (MP7), and reason abstractly and quantitatively (MP2) by applying their understanding of properties of operations on numbers to algebraic expressions.

### Learning Goals

Teacher Facing

• Practice determining whether a value is a solution of an equation in one variable.
• Review properties of operations on real numbers that result in equivalent expressions.

### Student Facing

• Let’s rewrite equations without changing their value.