The perimeter of a rectangle is 56m, and its length is 15m. What is the area of the rectangle?
长方形周长56m，长是15m，长方形面积是多少？
<gadget id="calculator">56 / 2</gadget>
<output>28</output>

<gadget id="calculator">28 - 15</gadget>
<output>13</output>

<gadget id="calculator">15 * 13</gadget>
<output>195</output>

<result>195</result>