Shantel 's rare book collection contains 40 books. she donates 15% of her books to the national library, sells 3/5 of her books on the Internet. How many books remain in shantel's book collection?

Shantel donates 15% of the 40 books to the national library.

40 (.15) = 6

She also sells 3/5 of the 40 books or 60% of it.

3/5 = x/40

Cross multiply

3 (40) = 5x

120 = 5x

Divide both sides by 5

x = 24

24 + 6 = 30

Subtract the number of books she sold or donated

40 - 30 = 10

Shantel has 10 books left in her book collection.