A classroom is 10 meters long and its width is 3 meters shorter than its length. What is the perimeter of the classroom in meters?
一个教室长10米，宽比长短3米，这个教室的周长是多少米？
<gadget id="calculator">10 - 3</gadget>
<output>7</output>

<gadget id="calculator">7 + 10</gadget>
<output>17</output>

<gadget id="calculator">17 * 2</gadget>
<output>34</output>

<result>34</result>