Xiao Ming reads a book, read (2/5) on the first day, read the rest (2/3) on the second day, and read 20 pages on the third day, just finished reading this book, then this book How many pages are there in total?
小明读一本书，第一天读了(2/5)，第二天读了剩下的(2/3)，第三天读了20页，正好读完这本书，则这本书一共有多少页．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1 - (2/3)</gadget>
<output>1/3 = around 0.333333</output>

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

<gadget id="calculator">20 / (1/5)</gadget>
<output>100</output>

<result>100</result>