Answer: OPTION B.
Explanation:
The equation of the line in Slope-Intercept form is:

Where "m" is the slope and "b" is the y-intercept.
Given:

You can identify that its slope is:

By definition, the slope can be calculated with this formula:

Then, in order to find the slope of g(x), you can pick the points (2,-8) and (6,4) and say that:

So, substituting these values into the formula, you get:

If you subtract the slopes, you get that the positive difference between them, is:
