The perimeter of a rectangle is 18 cm, the width is 3 cm, what is the length
一个长方形的周长是18厘米，宽是3厘米，长是多少
<gadget id="calculator">18 / 2</gadget>
<output>9</output>

<gadget id="calculator">9 - 3</gadget>
<output>6</output>

<result>6</result>