This module contains a brief presentation of matrices and common operations associated with matrices. The discussion includes matrix addition, subtraction, and multiplication. We demonstrate how to represent a system of equations with matrix notation. This is used with the linear programming simplex algorithm in Module 7. We show how determinants are used in finding the inverse of a matrix and solving a series of simultaneous equations. Interchanging the rows and columns of a matrix results in the transpose of that matrix. Cofactors and adjoints are used to develop the inverse of a matrix.