University of Georgia
University of Georgia: Slope of Lines
This site provides a detailed unit on finding the slope of lines that investigates methods for solving systems of equations. Good lesson plan for class.
Oak Ridge National Laboratory
Ornl: 7 Gaussian Elimination on Band Matrices
This site gives an example of solving a system of equations with the use of Gaussian Elimination.
Purple Math
Purplemath: Systems of Non Linear Equations: Definitions
This Purplemath lesson provides formulas, equations, graphs and explanations of systems of equations.
Wolfram Research
Wolfram Math World: Gaussian Elimination
This site provides an example of Guassian Elimination and concludes with a specific example.
Math Medics
S.o.s. Math: Application of Determinant to Systems: Cramer's Rule
This lesson explains how the determinant is used for Cramer's Rule.
National Council of Teachers of Mathematics
The Math Forum: Ask Dr. Math: Cramer's Rule in Action
This site provides a specific example of Cramer's Rule. The site does not explain why Cramer's Rule works, yet does a fair job of expressing the method to reach the answers.