Algebra question

Question

Arturo starts with 2457 comic books. He sells the same number every week, and after 18 weeks, he has only 357 left. How many comic books does he have after x weeks?

Answer 1

Arturo starts with 2457 comic books.  After 18 weeks, he is left with 357, and we know he sold the same number every week, so we can take the difference between his initial and final number of books, 2457 - 357 = 2100.  Arturo sold 2100 books over a period of 18 weeks.  To find the number of books he sold per week, we can divide 2100 by 18 and we get 116.67 books (this should be a whole number because he did not sell fractions of a book).  

 

If we were to write an expression for the amount of books Arturo has left after x number of weeks, it would be 2457 - 116.67x.