Two lengths of iron wire are equal, the first length is 1.8 meters, and the second length is 2.5 meters. The remaining first length is twice as long as the second length. What is the original length of the first length?
两段长度相等的铁丝，第一段用去1.8米，第二段用去2.5米，余下的第一段正好是第二段的2倍，第一段铁丝原来长多少．
<gadget id="calculator">2 * 2.5</gadget>
<output>5</output>

<gadget id="calculator">5 - 1.8 - 0</gadget>
<output>3.2</output>

<gadget id="calculator">2 - 1</gadget>
<output>1</output>

<gadget id="calculator">3.2 / 1</gadget>
<output>3.2</output>

<result>3.2</result>