This document discusses solving systems of three linear equations with three variables. It introduces Gaussian elimination as a method for solving such systems. Gaussian elimination involves eliminating variables one at a time to solve for the remaining variables in reverse order. The document provides an example of using Gaussian elimination to solve a 3x3 system. It also discusses the different outcomes possible for 3x3 systems, such as a single solution, infinitely many solutions, or no solution if the system is inconsistent or dependent.