Then half of bookcase A is (1+1/2) x.

A quarter less than the bookshelf is (1-1/4) × (1+1/2) x.

x+( 1+ 1/2)x+( 1- 1/4)×( 1+ 1/2)x = 2900

( 1+ 1+ 1/2+3/4×3/2)x = 2900

29/8×x=2900

x=(2900×8)÷29

x=800

( 1+ 1/2)x = 3/2×800 = 1200

( 1- 1/4)×( 1+ 1/2)x = 9/8×800 = 900

A: Shelf A has 1200 books, shelf B has 800 books and shelf C has 900 books.