rope is cut off by 1/5 of its full length for the first time, and 6 meters is cut off for the second time. At this time, half of the full length remains. What is the original length of the rope?
一根绳子第一次剪去全长的(1/5)，第二次剪去6米，这时还剩全长的一半，这根绳子原长多少米．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/2) - (1/5)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">6 / (3/10)</gadget>
<output>20</output>

<result>20</result>