In this lesson, Julie Harland shows how to solve a system of linear equations with three variables using the substitution method. She starts by solving for one variable in one of the equations, and then plugging it into the other equations to eliminate that variable. She then uses a combination of the addition and substitution methods to get two equations with two variables, which can be solved using either method. Finally, she plugs in those values to the original equations to check the solution. The lesson includes a detailed explanation of each step and is easy to follow along.
This video shows how to solve a system of 3 three linear equations in 3 variables using the substitution method, and also partly the addition (elimination) method to solve a system of 2 equations. The same problem is solved in the first part of this lesson series using the Addition Method.
More free YouTube videos by Julie Harland are organized at http://yourmathgal.com