A certain hotel receives a group of guests, if each room accommodates 2 persons, only 36 rooms are needed; if each room accommodates 3 persons, how many fewer rooms can be used?
某酒店接待一批客人，如果每间客房住2人，只需要36间客房；如果每间客房住3人，可以少用几间客房？
<gadget id="calculator">2 * 36</gadget>
<output>72</output>

<gadget id="calculator">72 / 3</gadget>
<output>24</output>

<gadget id="calculator">36 - 24</gadget>
<output>12</output>

<result>12</result>