Xiao Ming reads a book, and has read 30 pages, and the rest of the book (13/18) has not been read. How many more pages do I have to read to finish?
小明读一本书，已经读了30页，还剩下全书的(13/18)没有读．还要读多少页才能读完？
<gadget id="calculator">13 / 18</gadget>
<output>13/18 = around 0.722222</output>

<gadget id="calculator">1 - (13/18)</gadget>
<output>5/18 = around 0.277778</output>

<gadget id="calculator">30 / (5/18)</gadget>
<output>108</output>

<gadget id="calculator">108 - 30</gadget>
<output>78</output>

<result>78</result>