Since the slope is falling, instead of rising, it would be negative.
Now, on the line, I plotted (0, 2) and (-2, 10).
You would now plug this into the rise/run formula.
The formula is [tex] \frac{y2 - y1}{x2 - x1} [/tex]
The equation would become,
[tex] \frac{10 - 2}{-2 - 0} [/tex] = [tex] \frac{8}{-2} [/tex] = -4
I believe the answer would be -4.
I hope this helps!