This Instructional Activity is a part of the Lesson 6, Unit 6, Grade 6. Throughout this unit students have been matching equations to tape diagrams, matching equations to situations, and solving equations. This lesson shifts the focus to writing the expressions that describe situations with an unknown quantity. Students use operations to calculate quantities and notice repeated patterns in those calculations. They replace a part of the calculation with a letter to represent any possible value and create an expression that represents the situation. Students learn that they can use these expressions to answer questions about specific values.