After 20% of a rope is used up, there are 24 meters left. How many meters is this rope?
一根绳用去20%后，还剩24米，这根绳有多少米？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">24 / (4/5)</gadget>
<output>30</output>

<result>30</result>