Hang Hang read "Dinosaur World", an average of 28 pages per day, and after 18 days of reading, he found that there were still 57 pages that he hadn't read. How many pages does this "Dinosaur World" have?
航航读《恐龙世界》，平均每天读28页，读了18天，发现还有57页没读，这本《恐龙世界》共有多少页？
<gadget id="calculator">28 * 18</gadget>
<output>504</output>

<gadget id="calculator">504 + 57</gadget>
<output>561</output>

<result>561</result>