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?

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