There is a rectangle with a perimeter of 36 decimeters and a length of 12 decimeters. What is the area of this rectangle?
有一个周长是36分米的长方形，长12分米，这个长方形的面积是多少平方分米？
<gadget id="calculator">36 / 2</gadget>
<output>18</output>

<gadget id="calculator">18 - 12</gadget>
<output>6</output>

<gadget id="calculator">12 * 6</gadget>
<output>72</output>

<result>72</result>