The length of a rope is equal to (2/7) of its own length plus (2/5) meters, how many meters is the length of the rope?
一根绳子的长度等于它本身长度的(2/7)加上(2/5)米，这绳子长多少米．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">1 - (2/7)</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">(2/5) / (5/7)</gadget>
<output>14/25 = around 0.56</output>

<result>14/25 = around 0.56</result>