An interior decorator purchased a painting for $95, a sofa for $225, a chair for $275, and an end table for $155. the tax was $60 and delivery was $75. if she paid for the furniture with $50 bills, how many bills were needed?

To answer this question, we must assume that she will be overpaying the amount if it passes any multiple of 50$ ie. Can't pay 60$ with a 50$ bill.

So we add all the costs:
$95 + $225 + $275 + $155 + $60 + $75 = $885

We divide out 885 by 50, to see how many 50$ bills we need.
885 / 50 = 17 bills with Remainder of 35.
Since we still need to pay for the 35, we need an additional $50 bill.

Thus: 17 + 1 = 18 bills.