The length of the rectangle is 15 meters and the width is 3 meters less than the length. What is the perimeter of the rectangle?
长方形的长是15米，宽比长少3米，长方形的周长是多少米
<gadget id="calculator">15 - 3</gadget>
<output>12</output>

<gadget id="calculator">12 + 15</gadget>
<output>27</output>

<gadget id="calculator">27 * 2</gadget>
<output>54</output>

<result>54</result>