conversations.from: human
conversations.value: Break down this math problem: Melody has three dogs. Each dog eats 1/2 of a pound of dog food twice a day. If Melody bought 30 pounds of dog food, how many pounds of dog food are left after a week?
conversations.from: assistant
conversations.value: Each dog eats 1/2 x 2 = 1 pound of dog food each day.
  So the three dogs eat a total of 1 x 3 = 3 pounds each day.
  That is 3 x 7 = 21 pounds in a week.
  Therefore, 30 - 21 = 9 pounds of food are left after a week.