To build a canal, (3/4) has been built, and there are 18 kilometers left. How long is this canal?
修一条水渠，已经修了(3/4)，剩下18千米，这条水渠有多长？
<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">18 / (1/4)</gadget>
<output>72</output>

<result>72</result>