Xiaohong reads a book. After reading a part, the ratio of pages she has read to pages she has not read is 2:5. She reads another 36 pages. At this time, the ratio of pages she has read to pages she has not read is 3: 4. How many pages does this book have?
小红看一本书，看了一部分后，已看的和未看的页数比是2：5，她又看了36页，此时，已看的和未看的页数比是3：4．这本书共有多少页？
<gadget id="calculator">2 + 5</gadget>
<output>7</output>

<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">(3/7) - (2/7)</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">36 / (1/7)</gadget>
<output>252</output>

<result>252</result>