3. There are a total of 450 books on three bookshelves, A, B, and C. If 60 books are taken from A and placed in B, then 20 books are taken from B and placed in C, and finally 30 books are taken from C and placed in A, the number of books on each bookshelf will be equal. The original number of books on bookshelf A is _ books.
【Analysis】The final number of books is equal to: $450 \div 3=150$ (books) A: $(180) \xrightarrow{-60}(120) \xrightarrow{+30}(150)$