Helpp me please (No Links Or Files For Explanations Or Solutions)

Thank you very much in advance for whom will help and for whom will answer my questions correctly.​​

1. Is addition property of equality
2 one is (a) which is 3a.3b

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.