This is simple as all you have to learn is what slope intercept form is and how it works. In SIF, the number paired with the x is the slope, which should always be put over 1 if it is not already put over another number. The slope is the "rise over the run" which means that it is a proportion. For every 4 that you go up in this case, you should be moving over 1 on the x axis. The other number (-5) is the y-intercept, which means that the line you draw at the slope should go through that number.
In the attached image, the y-intercept (-5) is highlighted and the blue dots shows that the line goes up 4 and over 1 (slope) between each point.