What is 5x4-3x-5 i'm not so good with decimals

It has nothing to do with decimals all you have to do is "box out" as I do and you combine the 5x and the negative 3x seperate from the 4 minus 5 and the awnser should be 2x minus 1

Its algebra 

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.