A wire is cut off (5/7), and the rest is 18 meters shorter than the cut one. How many meters to cut off?
一根电线截去(5/7)，余下的比截去的短18米．截去多少米？
<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">1 - (5/7)</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">(5/7) - (2/7)</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">18 / (3/7)</gadget>
<output>42</output>

<gadget id="calculator">42 * (5/7)</gadget>
<output>30</output>

<result>30</result>