Xiao Ming reads a book. He read 20 pages on the first day, and the number of pages he read on the second day is the first day (9/10), and he read this book in two days (19/40). How many pages are there in this book? Page?
小明读一本书，第一天读了20，第二天读的页数是第一天的(9/10)，两天读了这本书的(19/40)，这本书共有多少页？
<gadget id="calculator">9 / 10</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">20 * (9/10)</gadget>
<output>18</output>

<gadget id="calculator">20 + 18</gadget>
<output>38</output>

<gadget id="calculator">19 / 40</gadget>
<output>19/40 = around 0.475</output>

<gadget id="calculator">38 / (19/40)</gadget>
<output>80</output>

<result>80</result>