The perimeter of a rectangle is 60 decimeters and the length is 18 decimeters. What is the area of the rectangle?
一个长方形的周长是60分米，长是18分米，这个长方形的面积是多少平方分米？
<gadget id="calculator">60 / 2</gadget>
<output>30</output>

<gadget id="calculator">30 - 18</gadget>
<output>12</output>

<gadget id="calculator">18 * 12</gadget>
<output>216</output>

<result>216</result>