Question

Lily bought 6 new compact disks and 2 used compact disks for $127.92. At the same prices, Mackenzie bought 3 new compact disks and8 used compact disks for $133.89. Find the cost of buying a single used compact disk.

Use substitution method

Answer 1

Answer:

Step-by-step explanation:

Let cd=x

& Used cd=y

So,

6x+2y=127.92...........1

3x+8y=133.89...........2

Now, from 1, we can say that x=127.92-2y/6

Putting value of x in 2

3(127.92-2y/6)+8y=133.89

(127.92-2y/2)+8y=133.89

63.96-y+8y=133.89

7y=69.93

y=9.99

So, price of used cd is $9.99