One wire is (3/4) kilometers long, (1/4) is used up, how much is left
一根是(3/4)千米长的电线，用去了(1/4)，还剩下多少
<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>