The perimeter of a rectangle is 48 meters, the width is 4 meters, what is the length in meters?
长方形的周长48米，宽4米，长是多少米．
<gadget id="calculator">48 / 2</gadget>
<output>24</output>

<gadget id="calculator">24 - 4</gadget>
<output>20</output>

<result>20</result>