conversations.from: human
conversations.value: Alicia has to buy some books for the new school year. She buys 2 math books, 3 art books, and 6 science books, for a total of $30. If both the math and science books cost $3 each, what was the cost of each art book?
  Give me a clear explanation.
conversations.from: assistant
conversations.value: The total cost of maths books is 2*3 = 6 dollars
  The total cost of science books is 6*3 = 18 dollars
  The total cost for maths and science books is 6+18 = 24 dollars
  The cost for art books is 30-24 = 6 dollars.
  Since he bought 3 art books, the cost for each art book will be 6/3 = 2 dollars