Math Planet
Math Planet: The Substitution Method for Solving Linear Systems
A way to solve a linear system algebraically is to use the substitution method. The substitution method functions by substituting the one y-value with the other. This resource explains this method by showing an example along with a video.
Khan Academy
Khan Academy: Substitution Method Review (Systems of Linear Equations)
This article will take you through a step-by-step approach for solving a systems of linear equations. Article also includes practice questions.