The family purchased regular tickets for $9 each, so the total cost of the regular tickets is $9 x 2 = $18.
The children's tickets are $2 less than the regular tickets, so the cost of each children's ticket is $9 - $2 = $7.
The family gave the cashier two $20 bills, so they paid a total of $20 x 2 = $40.
After purchasing the tickets, they received $1 change, so the total cost of the tickets is $40 - $1 = $39.
The cost of the regular tickets is $18, so the cost of the children's tickets is $39 - $18 = $21.
Since each children's ticket costs $7, the family has $21/$7 = 3 children.
Therefore, there are 3 children in the family.
#### 3
The answer is: 3
Below is a math problem. Provide a detailed, step-by-step solution.

### Problem:
If the family gave the cashier two $20 bills and received $1 change after purchasing regular tickets for $9 each and children's tickets for $2 less, and there are 2 adults in the family, how many children are there in the family?

### Answer:
