These lines are parallel since they both have the slope of 3. Then it becomes a matter of seeing how far their y-intercepts are from one another. That is the distance between them, and will be the distance between them for the entire length of each line since parallel lines remain the same distance apart forever. The first line has a y-intercept of 6 and the second line has a y-intercept of -2. From 6 to 0 is 6, then add another 2 units to get a grand total of 8 units apart. Since distance is a measure of length and length will never be negative, we are not subtracting here. We are simply counting the number of units between each y-intercept. And it doesn't have to be the y-intercept. Every point on the first line is 8 units above every point on the second line.
