To build a canal of (7/3) km, (3/4) has been built, how many km is left.
修一条(7/3)km的水渠，已经修了(3/4)，还剩多少km．
<gadget id="calculator">7 / 3</gadget>
<output>7/3 = around 2.333333</output>

<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">1 - (3/4)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(7/3) * (1/4)</gadget>
<output>7/12 = around 0.583333</output>

<result>7/12 = around 0.583333</result>