The perimeter of a rectangle is 18 cm, the width is 4 cm, what is the length in cm?
一个长方形的周长是18厘米，宽是4厘米，长多少厘米．
<gadget id="calculator">18 / 2</gadget>
<output>9</output>

<gadget id="calculator">9 - 4</gadget>
<output>5</output>

<result>5</result>