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.
[tex]18x + \dfrac{35}{x}[/tex]
[tex]= \dfrac{18x^2}{x} + \dfrac{35}{x}[/tex]
[tex]= \dfrac{18x^2 + 35}{x}[/tex]
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.
