Question

Music CD's cost $9 each, and movies cost $10 each. If you

spend $78 and buy 8 items, how many of each did you buy?

Answer 1

2 CDs and 6 movies

Explanation:

Let the number of CD you bought be x, and the number of movies you bought be y.

Since you bought 8 items in total,

x + y = 8 ______(1)

The sum of money spent is 78, so

9x + 10y = 78 ________(2)

From equation (1),

x = 8 - y ________(3)

Substitute (3) into (2),

9 (8-y) + 10y = 78

72 - 9y + 10y = 78

- 9y + 10y = 78-72

y = 6

Now substitute y=6 into (3).

x = 8 - y

x = 8-6

x = 2

Therefore, you bought 2 CDs and 6 movies.