How do chapters 8 and 9 develop aristotle’s conception of the mean?

The mean is a spot between two extremes, though one extreme is worse than the other. It is difficult to find one must have the right tools, and that's why virtue is rare. You don't just find it by wishing it. Aristotle makes the case that the mean is a very real concept which requires one to accurately evaluate both extremes and the range between then find the appropriate action or understanding, the median and aim/pattern actions in that direction. These chapters explain this concept.