Answer:
here you go mate
you would just plug in the formulas given to you following the hint it's:
r(n) - c(n)
which goes to
65n - (4n + 5500)
then we can simplify that to
61n - 5500
Part 2:
61(850) - 5500
51850 - 5500 = 46350
this means if he sells 850 tickets he will make a net of 46350 dollars