If the perimeter of a rectangle is 12 cm and its length is 4 cm, what is the width of the rectangle?
一个长方形的周长是12cm，它的长是4cm，那么这个长方形的宽是多少
<gadget id="calculator">12 / 2</gadget>
<output>6</output>

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

<result>2</result>