Ding Ding reads a book and has already read (2/7), and after reading 54 pages, he has finished reading 80% of the book. How many pages does this book have?
丁丁读一本书，已经读了(2/7)，再读54页就读完了全书的80%．这本书一共有多少页？
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">(4/5) - (2/7)</gadget>
<output>18/35 = around 0.514286</output>

<gadget id="calculator">54 / (18/35)</gadget>
<output>105</output>

<result>105</result>