Even two points are enough to plot a line. Just pick two points (x1,y1), (x2,y2) that satisfy the equation 2y=3x+11, for example x=1,y=7 and x=0,y=5.5.
Then plot them on the plane, and connect the two dots to get your line.
Every month the number of orders in goes up by 2 and the number of orders out goes up by 1 so that means they are taking in more orders than they are sending out.