A 20-meter-long iron wire uses up 5.65 meters for the first time and 3.45 meters for the second time. Please ask a mathematical problem and solve it.
一根20米长的铁丝，第一次用去5.65米，第二次用去3.45米．请你提出一个数学问题并解决问题．
<gadget id="calculator">5.65 + 3.45</gadget>
<output>9.1</output>

<gadget id="calculator">20 - 9.1</gadget>
<output>10.9</output>

<result>10.9</result>