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.

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

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step-by-step explanation: