ANSWER
60 paperback books
EXPLANATION
We have that:
Paperback books sell for $1.00
Hardback books sell for $5.00
The store sold 100 books and made $260.
Let the number of paperback books be x
Let the number of hardback books be y.
This means that:
x + y = 100 _____(1)
and
1 * x + 5 * y = 260
=> x + 5y = 260 ____(2)
We have two simultaneous equations:
x + y = 100 ____(1)
x + 5y = 260 ___(2)
From (1):
x = 100 - y
Put that in (2):
100 - y + 5y = 260
=> 100 + 4y = 260
Collect like terms:
4y = 260 - 100
4y = 160
y = 160 / 4
y = 40 books
This means that:
x = 100 - 40
x = 60 books
Therefore, 60 paperback books were sold.
