In this lesson, students write expressions with one variable to represent situations in which a calculation can be carried out repeatedly with different numbers. Students build on their work in prior grades and units with writing expressions to represent operations, situations, and relationships. In the previous section, students identified equations with variables that represented diagrams and situations. They also wrote equations in percent situations where the equation structure was clearly stated (  of equals ). Now, students practice interpreting situations, writing expressions with a variable, and explaining how the parts of the expression match the situation. Students complete tables and write both numerical and algebraic expressions.

Throughout the lesson, as students perform the same calculations and generalize relationships with algebraic expressions, they practice expressing regularity through repeated reasoning (MP8). They are also encouraged to attend to precision when describing how their expressions relate to situations, using the vocabulary they developed in previous lessons (MP6).