conversations.from: human
conversations.value: The length of the straight part of a river is three times shorter than the crooked part. If the river is 80 miles long, how long is the straight part of the river?
  Solve this problem.
conversations.from: assistant
conversations.value: Let's say the river's length in the straight part of the river is x.
  The total length of the river is the length of the straight part plus 3 times the length of the straight part for the crooked part, which is x+3x = 80
  The total length of the river is 4x=80
  The straight part of the river is x=80/4 = 20 miles.