1. The document presents three systems of equations related to word problems involving Justin and Karin's allowance, costs for recreation programs, and ages of Dewan and Adrianne. 2. Graphs are helpful for solving systems of equations because they allow you to visually check solutions obtained through algebraic methods. Graphing the equations shows their point of intersection, which indicates the solution. 3. Learning to solve systems of equations algebraically and using graphs helps answer word problems leading to two linear equations in two variables, as required by the Common Core standards.