# Lesson 15

Off the Line

These materials, when encountered before Algebra 1, Unit 2, Lesson 15 support success in that lesson.

### Lesson Narrative

In this lesson, students practice finding simpler, equivalent equations in order to solve for an unknown. In the row game, students notice that multiplying an equation by a number results in the same answer for the unknown. In the other activity, students follow a plan to determine the weights of two different items by finding the weights of different groupings and combining their weights.

Students use tools strategically (MP5) if they choose to manipulate physical items to represent the items being weighed in the second activity. Students reason abstractly and quantitatively (MP2) when they find the ways to create the appropriate groupings to solve for the weight of a single item.

### Learning Goals

Teacher Facing

• Recognize that a multiple of an equation has the same solution as the original equation.
• Use a concrete example to recognize moves that can be done to a system of equations without changing the solution.

### Student Facing

• Let’s study solutions and non-solutions.

### Required Preparation

Provide access to two different types of items to represent nickels, dollar coins, plastic bricks, and number cubes.