conversations.from: human
conversations.value: Can you explain how to solve this math problem: There are 50 marbles in a box which has a mixture of white, red and blue marbles. There were originally 20 white marbles and an equal number of red and blue marbles. Jack removes a number of marbles equal to double the difference between the number of white marbles and the number of blue marbles. How many marbles are left in the box?
conversations.from: assistant
conversations.value: 20 of 50 marbles are white so there are 50-20 = 30 red and blue marbles
  The number of red marbles and blue marbles is the same, so there are 30/2 = 15 of each color
  The difference between the number of white marbles and blue marbles is 20-15 = 5
  Double the difference is 5*2 = 10 marbles
  10 marbles are removed to leave 50-10 = 40 marbles