Question 1070900
i believe what you call the crossing graphs method is simply the intersection of the graphs of each equation.


your two equations are:


-9x +21y = 79
13x + 17y = 4


graph each equation on the same graph and then find out where the graph of both equations intersects.


your graph would look something like this:


<img src = "http://theo.x10hosting.com/2017/030101.jpg" alt="$$$" </>


note that some graphing software allows you to enter the equations as is and others require you to solve for y.


i did it both ways as shown on the graph.


there are two equations for the red graph and two equations for the blue graph.


since the equations are identical, the same line is drawn for both equations of the same color.