After (1/4) of the (3/7) meter long iron wire is used up, how much of it is left.
(3/7)米长的铁丝用去它的(1/4)后，还剩它的多少．
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<result>3/4 = around 0.75</result>