There are 12 boxes of pens in a box, there are 15 boxes of pens in the store, some are sold, and there are 3 boxes left, how many pens were sold?
一盒钢笔有12支，商店里有15盒钢笔，卖了一些，还剩3盒，卖了多少支钢笔？
<gadget id="calculator">15 - 3</gadget>
<output>12</output>

<gadget id="calculator">12 * 12</gadget>
<output>144</output>

<result>144</result>