conversations.from: human
conversations.value: A family went out to see a movie. The regular ticket costs $9 and the ticket for children is $2 less. They gave the cashier two $20 bills and they received a $1 change. How many children are there if there are 2 adults in the family?
conversations.from: assistant
conversations.value: They gave the cashier $20 x 2 = $40.
  Since a $1 change was returned, this means the tickets cost $40 - $1 = $39.
  Two adult tickets cost $9 x 2 = $18.
  So, $39 - $18 = $21 was spent for the children's tickets.
  Each child's ticket costs $9 - $2 = $7.
  Therefore, there are $21/$7 = 3 children.