A rope is (5/7) meters long, if (2/5) of it is used up, how many meters are left?
一根绳子长(5/7)米，用去它的(2/5)，还剩多少米．
<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

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

<result>3/7 = around 0.428571</result>