Answer:
Sean is wrong
Step-by-step explanation:
Slope tell the rate of the steepness of a line. Slope just telling you the rate, not the distance. You can't average the slope of two lines because the length of the line can be different.
Let's say A at (0, 0) and B (100, 200) and C at (101, 206). These coordinate fulfill the slope said above, but the slope of AC is 206/101= 2.04.
Sean can be right, but only if the horizontal length(x-axis distance) of AB=BC. If that so, using the example similar to above the coordinate can be A(0, 0), B(100, 200), C (200, 800). In this case, the slope is equal to the average of both lines.