Hi! I don't know much about stadistics, so I hope you can help me with this problem.

Consider the following numbers: 2, 3, 3, 4, 1, 2, 2, 1, 0 representing the number of hits garnered by each member of the Baltimore Orioles in a recent outing. (a) Calculate directly the average number of hits per man. (b) Let x be a variable signifying the number of hits obtained by a man, and let f(x) be the number of times the number x appears.

Show that the average number of hits per man can be written as:

Attachment 27210
The average number of hits per man is 2, am I right? However I don't know how to show part b). Thanks in advance.