The perimeter of a rectangle is 36 meters, the length is 12 meters, what is the area?
一个长方形的周长是36米，长是12米，面积是多少．
<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>