Write a story that could describe the expression: 75x - 20

If John wants to buy 75 packs of gum but doesn't know how much pieces of gum are in each pack as well as that he has to give 20 pieces to his friend Dan, how many pieces of gum does he have left? 

Since he adds x pieces of gum for each pack, his total gum is 75x. Next, since he gives 20 pieces to his friend, we have to subtract 20 from that

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.