One side of a parallelogram is 15 cm, and its adjacent side is 3 cm shorter than it. What is the perimeter of the parallelogram in cm?
一个平行四边形的一条边是15厘米，它的邻边比它少3厘米，这个平行四边形的周长是多少厘米？
<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>