In this optional lesson students write algebraic expressions to represent situations and solve equations. They are presented with problems that can be solved using grade 7 mathematics, but are often left for future grades when students have access to a wider variety of algebraic tools. Each of the situations described in the activities involve two or more unknown quantities and multiple relationships or actions. Initially students are walked through the steps of writing an expression to describe a situation, using properties to rewrite the expression with fewer terms, writing an equation to represent the situation, solving the equation, and considering the reasonableness of solutions. As they proceed through the lesson, the supports are slowly removed and students work on their own to reason through the problem (MP2). This lesson relies on skills developed in Unit 6.