What is the width of a rectangle with a circumference of 12 cm and a length of 4 cm?
周长12厘米的长方形，长4厘米，宽是多少厘米．
<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<gadget id="calculator">6 - 4</gadget>
<output>2</output>

<result>2</result>