A rope, use up the full length (1/3) for the first time, use up the full length (2/5) for the second time, use 2 meters more for the second time than the first time, how many meters is the rope ?
一根绳子，第一次用去全长的(1/3)，第二次用去全长的(2/5)，第二次比第一次多用去2米，这根绳子长多少米？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(2/5) - (1/3)</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">2 / (1/15)</gadget>
<output>30</output>

<result>30</result>