Sam invited 9 friends to a birthday party, but 6 couldn't come. If he wanted to buy enough cupcakes so each person could have exactly 2, how many should he buy?
<gadget id="calculator">9 - 6</gadget>
<output>3</output>

<gadget id="calculator">2 * 3</gadget>
<output>6</output>

<result>6</result>