th 8 Grade Math Lesson 5.2 Solving Systems of Linear Equations by Substitution Lesson 5.2 - Solving Systems of Linear Equations by Substitution Learning Target: Understand how to solve systems of linear equations by substitution. Success Criteria: - I can solve a linear equation in two variables for either variable. - I can solve a system of linear equations by substitution. Another way to solve a system of linear equations is to use substitution to obtain an equation in one variable.