Write a system of equations to describe the situation below, solve using substitution, and fill in the blanks.
Dr. Finley just got his PhD, and he wants to print copies of his thesis in hardcover book format. He could use Belmont Printing, paying a setup fee of $38 and $3 for every book printed. Alternately, he could go through Riverside University, paying an up-front fee of $29 and $6 per book. It turns out that, given the number of books Dr. Finley wants to print, the two options cost the same amount. How many books is that? What is the amount?
For ___ books, the cost is $___
.