In this lesson, students apply what they have learned about variables and equations to represent and solve real-world problems. Students must decontextualize the situation and represent it symbolically, and then interpret the results of any calculation in context. In doing so, they practice reasoning abstractly and quantitatively (MP2). 

Some students may use drawings or diagrams to help them reason about the situation and the relationships between the quantities. Others may dive straight into solving the problem with arithmetic only. Either case is an opportunity to help students see the parallel with representing and solving the problem algebraically using an equation.

As students represent real-world situations with equations, it is important for them to precisely state the meaning of the variable, including any units involved (MP6).