conversations.from: human
conversations.value: Brennan was researching his school project and had to download files from the internet to his computer to use for reference. After downloading 800 files, he deleted 70% of them because they were not helpful. He downloaded 400 more files but again realized that 3/5 of them were irrelevant. How many valuable files was he left with after deleting the unrelated files he downloaded in the second round?
  Find the solution.
conversations.from: assistant
conversations.value: The number of non-valuable files Brennan downloaded in the first round is 70/100*800 = 560 files.
  The number of valuable files Brennan downloaded in the first round is 800-560 = 240
  When he downloaded 400 new files, there were 3/5*400= 240 non-useful files, which he deleted again.
  The total number of valuable files he downloaded in the second round is 400-240 = 160
  To write his research, Brennan had 160+240 = 400 useful files to reference to write his research.