A wire used up 40% of its total length, leaving 18 meters. How long is this wire originally?
一根电线用去了全长的40%，还剩下18米．这根电线原来长多少米？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">18 / (3/5)</gadget>
<output>30</output>

<result>30</result>