What is the length of a rectangle in centimeters, the width of 2 centimeters, and the circumference of 18 centimeters.
一个长方形的长是多少厘米，宽是2厘米，周长是18厘米．
<gadget id="calculator">18 / 2</gadget>
<output>9</output>

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

<result>7</result>