Proportions:

an airplane boards 16 people every 3 minutes how long would it take to board all 150 passengers?

You would set up your proportion like this 16/3 = 150/x. then all you have to do is cross multiply both sections, so 16x = 450, then just solve for x, by dividing 450 by 16, which gives you x=28.125. 

In all honesty, there really is no “work” per say to show. mainly it’s just using the process of elimination. the question is asking which domain(s) would be the most appropriate for the function c(n). n is the number of observed vehicles so right away, 1, 2, and 3 can be eliminated.why? 1, 2 start in the negatives and therefore it is impossible to observe negative cars. so, #4 would be the best answer to the given problem.