The perimeter of the rectangle is 24 decimeters, the width is 5 decimeters, what is the length?
长方形的周长是24分米，宽是5分米，长是多少．
<gadget id="calculator">24 / 2</gadget>
<output>12</output>

<gadget id="calculator">12 - 5</gadget>
<output>7</output>

<result>7</result>