# Expressions and Equations / Visualizing Systems of Linear Equations

Activity 15 of 18
In this lesson students will reason about solutions to systems of equations while modeling the systems on mobiles.

## Planning and Resources

Objectives
Students should be able to write algebraic equations using variables that represent the relationship among the values of shapes on a mobile, associate moves that preserve balance in the mobile with moves that preserve algebraic solutions, and find solutions to systems of linear equations in more than one variable.

Vocabulary
equation
system of linear equations in two variables

Standard:

## Lesson Snapshot

#### Understanding

Students understand how mapping balanced mobiles to a system of equations provides a foundation for reasoning about strategies for solving systems of equations.

### What to look for

Some students may reason about the numerical value for each expression in an equation and how they must be the same, while others may reason by identifying numbers that make the mobile unbalanced and in which direction.

### Sample Assessment

"A store sells white scarves and red scarves. A white scarf costs $3 and a red scarf costs$5. On Monday, the store sold 12 scarves for a total of \$50. What is the total number of red scarves that the store sold on Monday?

a. 4
b. 5
c. 6
d. 7