If the perimeter of a rectangle is 18 decimeters and the width is 2 decimeters, what is its length?
一个长方形的周长是18分米，宽是2分米，那么它的长是多少分米．
<gadget id="calculator">18 / 2</gadget>
<output>9</output>

<gadget id="calculator">9 - 2</gadget>
<output>7</output>

<result>7</result>