A pile of coal weighs (3/4) tons, if (1/4) is used up, how many tons are left?
一堆煤重(3/4)吨，用去(1/4)，还剩多少吨．
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<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>

<gadget id="calculator">(3/4) * (3/4)</gadget>
<output>9/16 = around 0.5625</output>

<result>9/16 = around 0.5625</result>