There is a two-story bookshelf in the book corner of Class 5/KLOC-0. The number of books in the upper layer is 1.2 times that of the lower layer, and the lower layer has 9 fewer books than the upper layer. How many books are there?

9÷( 1.2- 1)×( 1.2+ 1)

=9÷0.2×2.2

=45×2.2

=99 copies