A wire first uses up (1/4) of the total length, and then uses up the rest (3/5), leaving 12 meters in the end. How long is the wire in meters?
一根电线，先用去了总长的(1/4)，又用去剩下的(3/5)，最后剩12米，这根电线原来长多少米？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(3/4) * (3/5)</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">1 - (1/4) - (9/20)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">12 / (3/10)</gadget>
<output>40</output>

<result>40</result>