At the 4:13 mark, the second equation is listed as x + 2y = 9, but it should say x + y = 9.
In this lesson, we are introduced to the concept of systems of equations, which are linear equations that can be written as lines. We learn that there are three methods for solving systems of equations: the graphing method, the substitution method, and the addition method. Using a brain teaser puzzle as an example, we see how to define variables and write equations to represent the problem. The lesson also includes a brief demonstration of how to solve the puzzle using each of the three methods, setting the stage for more in-depth tutorials on each method in subsequent videos.
Part I of Solving Linear Systems of Equations with 2 variables. Part 1 is an overview of how to solve systems
More free YouTube videos by Julie Harland are organized at http://yourmathgal.com