Shelby was having a movie party for her birthday. She and her mom made a dozen bags of buttered popcorn and 10 bags of caramel popcorn. Her brother Alan took 3 bags of buttered popcorn and 1 bag of caramel popcorn for his friends. How many bags of popcorn does Shelby have left for the party?
Shelby and her mom made 12 bags of buttered popcorn + 10 bags of caramel popcorn = 
<gadget id="calculator">12+10</gadget>
<output>22</output>
22 bags.
Of those 22 bags, her brother took 3 bags of buttered popcorn + 1 bag of caramel popcorn = 
<gadget id="calculator">3+1</gadget>
<output>4</output>
4 bags.
So now Shelby has 22 bags - 4 bags = 
<gadget id="calculator">22-4</gadget>
<output>18</output>
18 bags of popcorn left.

<result>18</result>