A piece of iron wire is used up (2/5) of its full length, and then 13 meters are connected. The current length of the iron wire is (1/4) longer than the original one. How many meters is the length of the used iron wire?
一根铁丝用去全长的(2/5)，再接上13米，现在的铁丝比原来长(1/4)，用去的铁丝长多少米？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(2/5) + (1/4)</gadget>
<output>13/20 = around 0.65</output>

<gadget id="calculator">13 / (13/20)</gadget>
<output>20</output>

<gadget id="calculator">20 * (2/5)</gadget>
<output>8</output>

<result>8</result>