1000+1500=2500 is how much she owes right now If each hat is sold for 12.50, all you have to do is 2500/12.50=200 She needs to sell 20 hats to break even.
She walked down 2 flights, then up 3 flights. This would cause her to be 1 floor above her floor. So, she would have to walk down 1 flight (hence the negative in the -1) and she would be on her floor.