This Instructional Activity is a part of the Lesson 8, Unit 4, Grade 7. In this activity, students are calculating percent increase and decrease in the context of interest and depreciation. They may have encountered these contexts before this unit, but be sure that everyone understands the basic idea of interest and depreciation before students begin work. Students have enough experience to solve these problems using various strategies and representations. Look for students writing different but correct expressions in terms of x.