To find the average, add the cost of each book to get a total cost, then divide the total cost by the number of books purchased.
Total cost: 32 + 45 + 39 = 116
Average cost: 116 / 3 = 38.67
As a practical equation, this one doesn't make much sense -- why would the profit per person have a term proportional to the number of people? Let's just go with it.



That's the answer to the first part.
35/x represents a portion of the profit that's 35/x per person, or a constant $35 per tour.
Private funding can run out. federal funding will likely not run out