The length of a rectangle is 18 decimeters, and its length is 6 times its width. What is its perimeter?
长方形的长是18分米，长是宽的6倍，它的周长是多少分米？
<gadget id="calculator">18 / 6</gadget>
<output>3</output>

<gadget id="calculator">18 + 3</gadget>
<output>21</output>

<gadget id="calculator">21 * 2</gadget>
<output>42</output>

<result>42</result>