1. The document provides examples for writing and solving systems of linear equations by graphing. It explains how to write equations in slope-intercept form, graph the lines on the same coordinate plane, and determine if the system has no solution, one solution, or an infinite number of solutions based on where the lines intersect. 2. Key steps shown include writing equations in y=mx+b form, finding the slope and y-intercept, graphing the lines and analyzing where they intersect to determine the number of solutions. 3. Graphing systems of equations allows you to visually see where lines intersect, satisfying both equations simultaneously and showing the solution to the system.