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?
They gave the cashier $20 x 2 = $
<gadget id="calculator">20*2</gadget>
<output>40</output>
40.
Since a $1 change was returned, this means the tickets cost $40 - $1 = $
<gadget id="calculator">40-1</gadget>
<output>39</output>
39.
Two adult tickets cost $9 x 2 = $
<gadget id="calculator">9*2</gadget>
<output>18</output>
18.
So, $39 - $18 = $
<gadget id="calculator">39-18</gadget>
<output>21</output>
21 was spent for the children's tickets.
Each child's ticket costs $9 - $2 = $
<gadget id="calculator">9-2</gadget>
<output>7</output>
7.
Therefore, there are $21/$7 = 
<gadget id="calculator">21/7</gadget>
<output>3</output>
3 children.

<result>3</result>