The perimeter of a rectangle is 26 cm, the width is 4 cm, and the length is in cm.
一个长方形的周长是26厘米，宽是4厘米，长是多少厘米．
<gadget id="calculator">26 / 2</gadget>
<output>13</output>

<gadget id="calculator">13 - 4</gadget>
<output>9</output>

<result>9</result>