When Xiao Ming reads a book, he is already optimistic about 60%, which is 80 pages more than the rest. How many pages is this book?
小明看一本书，已经看好60%，比剩下的多80页．这本书共多少页？
<gadget id="calculator">60 / 100</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 - (3/5)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(3/5) - (2/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">80 / (1/5)</gadget>
<output>400</output>

<result>400</result>