Answer:
Books remaining in Andrews book collection = 29 books
Step-by-step explanation:
Andrews book collection contains 60 books.
He donates 15% of his books to the national library,
Number of books to library = 60 x 15/100 = 9
Sells 1/4 of his books to a book dealer,
Book sold to book dealer = 60 x 1/4 = 15
Sells 7 books on amazon.
Books remaining = 60 - (9 + 15 + 7)
= 60 - 31
= 29
Books remaining in Andrews book collection = 29 books