Lesson objective: Apply systems of equations to solve real-world problems.

This lesson provides an opportunity for students to apply their knowledge and understanding of solving systems of equations to a real-life situation. Students are asked to complete a purchase order with missing values by solving a system of equations.

Key Concept students will use:

- Write an equation in one variable to solve a system of equations.

Skills students will use:

- substituting an equivalent expression for a variable
- writing an equivalent equation by applying properties of equality (Grade 7, Unit 6)
- solving an equation in one variable (Grade 7, Unit 6)

Students engage in Mathematical Practice 2 (reason abstractly and quantitatively) as they reason about the relationships between quantities in a problem and use the relationships to solve a problem.

**Key vocabulary: **

- equivalent equations
- equivalent expressions
- properties of equality
- substitution