Question

Abc bookstore sells new books, n, for $12, used books, u, for $8, and magazines, m, for $5 each. The store earned $340 revenue last month. The store sold 5 more used books than new books, and twice as many magazines as new books. Using substitution method, how many magazines, new books, and old books did ABC bookstore sell?

Answer 1

Answer:

The number of new books sold  =  10

The number of used books sold (u)   = 15

The number of magazines  sold (m) =   20

Step-by-step explanation:

Let us assume the number of new books  = n

So, the number of used books sold  (u)  = New books sold + 5 =  n + 5

Also, the number of magazines sold (m)  = 2 x ( Number of new books sold)  

= 2 n

⇒  u = n + 5, m = 2 n

Here, the cost of each new book  n-  = $12

So, the cost of n new books = n  x ($12) = 12 n

the cost of each used book  u  = $8

So, the cost of u = (n+ 5)  used  books = n+5  x ($8) = 8 n + 40

the cost of each magazine  m  = $5

So, the cost of m = (2n )  magazines = 2n  x ($5) = 10 n

Also, total earnings = $340

⇒ 12 n + 8n +40 + 10 n = 340

or,  30 n =  300

or,n = 300/30 = 10

Hence the number of new books sold  = n = 10

The number of used books sold (u)  = n + 5  = 15

The number of magazines  sold  = m = 2 n = 20