A pile of 3 tons of coal, use up (1/4) of the total amount, how much of the total amount is left
一堆3吨的煤，用去总数的(1/4)，还剩下总数的多少
<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>