60% of a book has been read, 80 pages more than the one that has not been read. How many pages are there in total?
一本书读了60%，比没读的多80页，这本书一共有多少页？
<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>