We want to draw a line representing the 'rise' and 'run' of the given line
Rise represents change in the y or vertical axis
Run represents change in the x horizontal axis
A portion of the graph representing the 'rise' and 'run' of the given line is shown below
Rise is the vertical line, AC
Run is the horizontal line, AD
The formula for calculating slope is
slope = rise/run
rise = 0 - 4 = - 4
run = - 2 - - 6 = - 2 + 6 = 4
slope = - 4/4
slope = - 1