posted by johnny .
Suppose you are starting an office-cleaning service. You have spent $315. To clean an office, you use $4 worth of supplies. You charge $25 per office. How many offices must you clean to break even?
I don't understand this. I just made an equation, 4x + 25y = 315.
Let's do it this way.
$25 - 4 = $21. This is your profit for one office.
$315 / $21 = 15
You'd have to clean 15 offices to break even.