Lesson objective: Solve realworld, multistep problems involving percent change by writing equations.
This lesson provides an opportunity for students to apply their knowledge and understanding of percent change to a reallife situation. Students are asked to calculate percent change through discounts and sales tax, as well as determining the final cost to the buyer. Students will then calculate the monthly payment to select the product with the lower price.
Key Concept students will use:

If we know any two values in the relationship "x percent of y" is z, we can find the third value.
Skills students will use:
 calculate percent increase or decrease by setting up an equation to represent the situation and solving for the missing value
 calculate the original value and the new value by setting up an equation to represent the situation and solving for the missing value
 calculating sales tax and discounts
Students engage in Mathematical Practice 1: Make sense of problems and persevere in solving real life, multistep mathematical problems involving percent by writing and solving equations to represent problems involving simple interest.
Key vocabulary:
 discount
 monthly payments
 percent change
 percent decrease
 percent increase
 sales tax
Special materials needed:
 calculators (as needed)
 graph paper