Gaussian Elimination
Interchange two equations
Multiply an equation by a non-zero constant
Add a multiple of one equation to another
Systematic Method
Save the x term in equation 1 and use it to eliminate all the other x terms below it via rk' = c r1 + rk
Ignore equation 1 and use the y term in equation 2 to eliminate all the
y terms below it.
Continue until the matrix is in echelon form
The last non-zero equation will yield xk=b, and then
back substitution can be used.