A linear equation solver takes a specified number of linear equations and solves them using established methods. Make sure to review what each program/website is capable of solving because each is slightly different.
Programs like Linear Equation Solver at algebra.com are only intended to solve one equation with one variable. If you need to solve more equations or more variables, WebMath has more answers depending on the level of expertise required. If neither of those sites has your needs covered, WIMS provides a system that not only allows you to customize your input but is also flexible enough to handle any system of linear equations.