conversations.from: human
conversations.value: Can you give me some step-by-step instructions for this math problem: There are 40 pupils in a class. Half of the class likes blue. One-fourth of the remaining likes green and the rest likes yellow. How many pupils like the color yellow?
conversations.from: assistant
conversations.value: There are 40/2 = 20 pupils who like blue.
  So, there are now 40 - 20 = 20 pupils who like either green or yellow.
  Hence, 20/4 = 5 pupils like green.
  Thus, 20 - 5 = 15 pupils like yellow.