Lesson objective: Extend understanding that mathematical relationships can be written as expressions and we can show the relationship between the expressions with an equation using variables to represent quantities.

Students bring prior knowledge of expressions from 6.EE.B.6. This prior knowledge is extended to equations as students write an equation using proportional expressions. A conceptual challenge students may encounter is understanding that expressions can be used as numbers to create an equation that represents a value.

The concept is developed through work with a table, which shows how a unit rate is a multiplicative relationship with the unknown.

This work helps students deepen their understanding of operations because we use multiplication to show the relationship between variables.

Students engage in Mathematical Practice 2 (Reason abstractly and quantitatively) as they make sense of a numeric relationship and represent that relationship as an algebraic equation.

**Key vocabulary:**

- equation
- expression
- ratio
- unit rate
- variable