question: Janet gets a job as a waitress.  She makes $10 an hour from wages and another $15 an hour from tips.  She wants to save up 20% of the cost of a $10000 car for a downpayment.  If she works 40 hours a week how many weeks will she need to work to save the down payment?
answer: She makes 10+15=$<<10+15=25>>25 an hour from working
  That means each week she makes 25*40=$<<25*40=1000>>1000
  She wants to make 10000*.2=$<<10000*.2=2000>>2000
  So she needs to work 2000/1000=<<2000/1000=2>>2 weeks
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