CCSS.Math.Content.8.EE.C.7b: Solve linear equations with rational number coefficients, including equations whose solutions require expanding expressions using the distributive property and collecting like terms.
CCSS.Math.Content.HSA-REI.B.3: Solve linear equations and inequalities in one variable, including equations with coefficients represented by letters.
Solving equations is a foundational skill needed in pre-algebra and algebra. Being able to solve a variety of equations enables students to analyze functional relationships.
Students need practice in solving equations in order to develop fluency in uncovering unknown values.
The Common Core State Standards say, "Explain each step in solving a simple equation as following from the equality of numbers asserted at the previous step, starting from the assumption that the original equation has a solution. Construct a viable argument to justify a solution method." In this activity students practice justifying each step of solving 2-step equations. The activity is designed for partners - one solves, one justifies - and then partner trade roles.