Use the two coordinate pairs (-2, 21) and (8, 8). As we go horizontally from the first to the second, the run (change in x) is 10 and the rise (change in y) is -13. Thus, the slope of the line through (-2, 21) and (8, 8) is m = rise / run = -13/10.
The equation of this line follows y - k = m(x - h):
