The perimeter of a rectangle is 16 cm, the width is 4 cm, what is the length in cm?
一个长方形的周长是16厘米，宽是4厘米，长多少厘米．
<gadget id="calculator">16 / 2</gadget>
<output>8</output>

<gadget id="calculator">8 - 4</gadget>
<output>4</output>

<result>4</result>