Cut a rope into three sections, the first section is 10.5 meters long, the second section is 9.3 meters long, and the third section is 5.8 meters less than twice the sum of the first two sections. How long is the third section?
把一根绳子截成三段，第一段长10.5米，第二段长9.3米，第三段比前两段的总和的2倍少5.8米．第三段长多少米？
<gadget id="calculator">10.5 + 9.3</gadget>
<output>19.8</output>

<gadget id="calculator">19.8 * 2</gadget>
<output>39.6</output>

<gadget id="calculator">39.6 - 5.8</gadget>
<output>33.8</output>

<result>33.8</result>