Chenggu David fitness center

It is known that if you take 30 books from the upper level and put them on the lower level, there are as many books on the two levels.

Available: the upper layer has 30×2 = 60 books more than the lower layer;

So the lower level has 60÷(2.5- 1) = 40 books, and the upper level has 40×2.5 = 100 books.