The range is the <em>biggest number</em> minus the <em>smallest number</em>. This makes sense. The range here is 81.3 - 9.4 = 71.9.
Next, see the two middle groups? You can see the median, 45.5. Does the left or right side seem more spread out? It's the right side. 34.7 is closer to 45.5 than 63.6 is to 45.5.
Each book costs 3 dollars and b is the number of books borrowed that one month. In that month, she also needs to pay 16 dollars for her membership so if you put all of it together, you get 3b + 16.