Question 254168
first you need to find out what profit you make on each office cleaned.
charges - expenses=earnings

then you need to find out how many offices it will take you to earn $315
earnings *x=315
or 
315/earnings=x
solve for x number offices to clean
if x is not a whole number (counting number) then raise it to the next whole number.
They won't pay you for cleaning part of an office.