A rectangle has a perimeter of 36 decimeters, a length of 12 decimeters, and a width of 12 decimeters.
一个长方形的周长是36分米，长12分米，宽是多少分米．
<gadget id="calculator">36 / 2</gadget>
<output>18</output>

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

<result>6</result>