12 willow trees are arranged in a row, and 3 peach trees are planted between every two willow trees. How many peach trees are planted in total?
12棵柳树排成一排，在每两棵柳树中间种3棵桃树，共种多少棵桃树．
<gadget id="calculator">12 - 1</gadget>
<output>11</output>

<gadget id="calculator">3 * 11</gadget>
<output>33</output>

<result>33</result>