conversations.from: human
conversations.value: Paul is working at a university. He is part of a big project, which involves 70 scientists in total. Half of them are from Europe and one-fifth are from Canada. The rest are from the USA. How many scientists in this project are from the USA?
  Solve this problem.
conversations.from: assistant
conversations.value: Of all the scientists taking part in the project, half of them are from Europe, which means 70 * 0.5 = 35 people.
  The number of researchers from Canada is 70 * 1/5 = 14 people.
  That means there are 70 - 35 - 14 = 21 researchers from the USA.