conversations.from: human
conversations.value: 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?
  Can you solve this problem?
conversations.from: assistant
conversations.value: 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=$45
  Two days later, the cost of filling each balloon was increased by $20 to $45+$20=$65
  If Bentley had 170 balloons that he wanted to fill, after the price increase, Bentley paid 170*$65=$11050 to fill 170 balloons.