Question 1189395
Assumption : Let z = 120 be the
totallity of all the books:
1/5(120) = 24 => no. of hardcover books
4/5(120) = 96 => no. of softcover books
2/3(120) = 80 => sold books, in w/c
3/4(24) = 18 are hardcover books
 of remaining hardcover books:
x = 24 - 18 = 6
of remaining books :
y - 120 - 80 = 40
let r be the fractional part of 
unsold books:
r = 6/40 = 3/20