Answer:
A - (20% of A) = 80% of A + (20% of (80% of A) = 96% of A
So if A is 100:
100 - (.2 * 100) = 80 + (.2 * 80) = 96
Step-by-step explanation:
Given is the number of science fiction books = 48
Let the number of mystery books be = x
Let the number of biographies be = y
Ratio of the number of mystery books to the number of science fiction books is 4:3 so
=

Ratio of the number of science fiction books to the number of biographies is 4:5 so 
=

Hence there are 48 science fiction books, 64 mystery books and 60 biographies.
So total number of books are = 
you could download 2 more songs.
X.59, where X stands for the number of songs downloaded, and .59 for the price of the song. 2*.59=1.18, or you could add .59+.59+.59=1.77, and 1.77 > 1.65, meaning you wouldn't afford the third song