conversations.from: human
conversations.value: I'm completely lost with this math problem: In the jar, there are 7 blue marbles, 11 red marbles, and some yellow marbles. If the chance of randomly picking a yellow marble is 1/4, how many yellow marbles are there?
  Can you give me a hand?
conversations.from: assistant
conversations.value: Let y be the number of yellow marbles
  There are 11+7+y=18+y total marbles.
  y/(18+y)=1/4.
  4y=18+y
  3y=18
  y=6
  There are 6 yellow marbles.