There are two piles of chess pieces, take (1/5) from the first pile to the second pile, the number of chess pieces in the two piles is exactly equal, then the original number of chess pieces in the second pile is the number of the first pile.
有两堆棋子，从第一堆拿(1/5)到第二堆，两堆的棋子数就正好相等，那么原来第二堆的棋子数是第一堆的多少．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

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

<result>3/5 = around 0.6</result>