If the perimeter of a rectangle is 24 meters and the width is 3 meters, what is the length in meters?
一个长方形的周长是24米，宽是3米，那么长多少米．
<gadget id="calculator">24 / 2</gadget>
<output>12</output>

<gadget id="calculator">12 - 3</gadget>
<output>9</output>

<result>9</result>