If the length of a rectangle is 7 decimeters and the width is 6 decimeters, what is its perimeter?
一个长方形的长是7分米，宽是6分米，它的周长是多少分米．
<gadget id="calculator">7 + 6</gadget>
<output>13</output>

<gadget id="calculator">13 * 2</gadget>
<output>26</output>

<result>26</result>