Astore is having a sale on dvds and cds. dvds cost $4 and cds cost $7. on one day, the store made $204 from dvd and cd sales, and sold a total of 39 items. write a system of equations, then solve to find how many dvds and cds were sold.

We are given here the individual costs of DVD and CD as well as the total sales and the number of items sold on one day. To solve the number of DVDs and CDs sold each, we devise two independent linear equations:

(1) x + y = 39
(2) 4x + 7y = 204

x- number of DVDs; y - number of CDs

solving, x= 23 DVDs
y = 16 CDs