Xiaofang loves to read. She reads a book about young heroes. After reading for a few days, the ratio of the number of pages she has read to the number of pages she has not read is 3:5. After she reads another 27 pages, the number of pages she has read is now The ratio to the number of unread pages is 9:7. How many pages does this book have?
小芳爱读书，她读一本少年英雄故事的书，读了几天后，已读页数与未读页数的比是3：5，后来又读了27页，这时已读页数与未读页数的比是9：7．这本书共有多少页？
<result>722</result>