question: On a certain day, the total cost of filling up 20 helium balloons was $900. Two days later, the cost of filling each balloon was increased by $20. How much did Bentley pay to fill 170 balloons if he went to fill them after the price increase?
answer: If the total cost of filling up 20 helium balloons was $900 before the price increase, the cost of filling one balloon was $900/20=$<<900/20=45>>45
  Two days later, the cost of filling each balloon was increased by $20 to $45+$20=$<<45+20=65>>65
  If Bentley had 170 balloons that he wanted to fill, after the price increase, Bentley paid 170*$65=$<<170*65=11050>>11050 to fill 170 balloons.
  #### 11050