The following lecture overheads and accompanying reading are independent of MatLab. Attaway Chapter 11.1 links matrices as described here with their representation and use in Matlab. Attaway 11.1 should be read and understood as a complement to the on-line lecture and reading.
Attaway 11.2, leading up to 11.2.2.1, gives the background and algorithm for Gaussian Elimination as a method of solving Linear Equations. It is useful "how-to" reading for the assignment.
[a1 b1] [x] = [c1] [a2 b2] [y] [c2]
[a11 a12 a13] [x1] [c1] [a21 a22 a23] [x2] = [c2] [a31 a32 a33] [x3] [c3]