The length of a rope is equal to (2/5) 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(2/5)加上(2/5)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 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(2/5) / (3/5)</gadget>
<output>2/3 = around 0.666667</output>

<result>2/3 = around 0.666667</result>