A used book store also started selling used CDs and videos. In the first week, the store sold a combination of 40 CDs and videos. They changed $4 per CD and $6 per video and the total sales were $180. Determine the total number of CDs and videos sold.

The total number of CDs sold is 30, and the number of videos is 10.

Step-by-step explanation:

Consider A is the number of Videos sold.

Consider B is the number of CDs sold.

So,

A + B = 40, B=40 - A

and

$6*A + $4*B=$180

Replacing, B=40 - A in the second equation

$6*A + $4 * (40 - A) = $180

Distributive property

$6A + $160 - $4A=$180

$6A - $4A=$180 - $160

$2A=$20

A=$20/$2=10

and B=40 - A, so B=40-10=30

That means, the number of Videos sold is 10

And the number of CDs sold is 30

number of CD's = 30

number of videos = 10

Step-by-step explanation:

The combined number of CD's and Videos sold is 40.

Let the

number of CD sold = a

number of video sold = b

The CD is sold $4 per CD. The videos is sold $6 per video. The combined sales was $180.

Combined number of CD and video

a + b = 40 ... (i)

Cost of the combined number of CD and video

4a + 6b = 180 ... (ii)

a + b = 40 ... (i)

4a + 6b = 180 ... (ii)

a = 40 - b

insert a in equation (ii)

4 (40 - b) + 6b = 180

160 - 4b + 6b = 180

160 + 2b = 180

2b = 180 - 160

2b = 20

divide both side by 2

b = 20/2

b = 10

insert b in equation (i)

a + b = 40 ... (i)

a + 10 = 40

a = 40 - 10

a = 30