It would be much easier to help if we had context!
However, for #1 it seems they have provided you opex in a % format. In which case, for every $ earned you have to spend x % in opex...this is the remaining operating profit (common term for looking at the profitability of a company)
You really need to study accounting 101!
For #2, again, case context would help, but it sounds like this highway company specifically charges per the km. So, they know when you enter the tollway, and when you exit, and calculate the fee you're charged. As such, it would make perfect sense to say "all the money will make will be based off how many cars enter the toolway and the average distance they drive"
This is not how all highway concessions work and is an important clarifying question at the beginning of the case.