Provide a scenario where you could have used a system of equations to solve a real world problem.

Picking a cell phone plan.  Say one plan charges .15 per minute with a flat fee of 30 a month.  Your charges would be C(x) = .15x + 30.  Another plan charges .40 per minute but only 10 for a flat fee.  That equation is C(x)=.40x+10. You could plot both these lines on the coordinate plane to see where the plans are equal (what number of minutes and dollars are the same) and then project which one would be better for you depending upon your usage.  Use the graph as a model to help you determine which is the better buy.