The length of a rectangle is 15 cm and the width is 3 cm shorter than the length. What is the perimeter of this rectangle in centimeters.
一个长方形的长是15厘米，宽比长短3厘米．这个长方形的周长是多少厘米．
<gadget id="calculator">15 - 3</gadget>
<output>12</output>

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

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

<result>54</result>