Standard 9.0 Solve a system of two linear equations in two variables algebraically and interpret the answer graphically; solve a system of two linear inequalities.
http://wn.com/Solving_Linear_Inequalities
If you can graph an inequality, you can graph a system of inequalities! This site will help you better understand Solving Systems of Linear Inequalities (SOLI).
Solving a system of linear equalities means to find a point (normally a single point) that satisfies both lines -- if you were to plot both lines, they could intersect and the point of intersection is the solution (that point is on both lines).
When would you need to use this standard?
You would probably use systems of inequalities in anything where you know a set of rates per object but not the number of objects (or vice versa) to find an answer can be made into this system.