Hey there!
I'll assume we're using the slope-intercept form equation:
y = mx + b
m = slope
b = y-intercept
First, we keep the y, because it's value depends on the x value given.
Next, we find the slope. Slope is defined as rise/run, so we take two points on the graph, find how much taller one is from another, and how far right/left they are, put those values over each other, and we have out slope (m).
Finally, we need to determine the y-intercept, and that's as simple as seeing where the line crosses the y axis and writing down that value.
Hope this helps!
The range is 13 because 115-102 is 13
