Thread: CD's

A DJ found a music store that had a great collection of used CD's. he purshased 38 CD's for a total of $235. The purchase included CD's priced at either $5.00 or $8.00. How many CD's in each price category did the DJ buy?

Originally Posted by wild_flowr69

A DJ found a music store that had a great collection of used CD's. he purshased 38 CD's for a total of $235. The purchase included CD's priced at either $5.00 or $8.00. How many CD's in each price category did the DJ buy?

Call the number of CDs bought at $5.00 x. Call the number of CDs bought at $8.00 y. We know that the total cost was $235, so:
.

Additionally, we know that 38 CDs were bought, so:
.

Two equations, two unknowns, so you can solve for x and y.

-Dan

Let me continue from topsquark's solution:
The equations

In the second equation solve for :

Substitute that into the first:

Now solve it,

Thus,

Thus,

Thus,