If you want to solve an optimization problem, you can use linear programming to help! This tutorial introduces linear programming and the different pieces of this method.
system of inequalities
Graph the solutions to a linear inequality in two variables as a half-plane (excluding the boundary in the case of a strict inequality), and graph the solution set to a system of linear inequalities in two variables as the intersection of the corresponding half-planes.
A system of equations is a set of equations with the same variables. A system of inequalities is almost exactly the same, except you're working with inequalities instead of equations! To solve such a system, you need to find the variable values that will make each inequality true at the same time. This tutorial will introduce you to systems of inequalities.