If (2/5) of a rope is used up, 6 meters are used up. If (2/3) of this rope is used up, how many meters are left?
一根绳，用掉它的(2/5)，用去了6米，如果用去这根绳的(2/3)，还剩多少米．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">6 / (2/5)</gadget>
<output>15</output>

<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1 - (2/3)</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">15 * (1/3)</gadget>
<output>5</output>

<result>5</result>