Store W gives you unlimited copies for 5 dollars, so the number of copies doesn't matter for store W, they do not affect the cost. So, you will have to find how many copies from store Z will cost 5 dollars. Now, it tells you store Z charges 2 dollars for the use of the machine, so you can go ahead and subtract 2 from 5 (total amount to make it equal). That being done leaves you with 3 dollars for the copies themselves, it tells you each copy costs $.20. So, now all you have to do is divide 3 by 0.20, which gives you 15.
