Xiao Ming reads a book. After reading for a few days, the ratio of the number of pages read to the number of unread pages is 2:3. After reading 56 pages, the ratio of the number of pages read to the number of unread pages is 5 : 4. How many pages does this book have?
小明读一本书，读了几天后，已读页数与未读页数的比是2：3，后来又读了56页，这时已读页数与未读页数的比是5：4，这本书共有多少页？
<gadget id="calculator">4 + 5</gadget>
<output>9</output>

<gadget id="calculator">5 / 9</gadget>
<output>5/9 = around 0.555556</output>

<gadget id="calculator">2 + 3</gadget>
<output>5</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(5/9) - (2/5)</gadget>
<output>7/45 = around 0.155556</output>

<gadget id="calculator">56 / (7/45)</gadget>
<output>360</output>

<result>360</result>