The perimeter of a rectangle is 12 decimeters, the length of this rectangle is 4 decimeters, what is the width?
一个长方形，周长是12分米，这个长方形的长是4分米，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>