A used book store also started selling used CDs and videos. In the first week, the store sold a comb

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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 charged $4 per CD and $6 per video and the total sales were $180. Determine the total number of CDs and videos sold

Let c be the number of CDs sold, and v be the number of videos sold. We're given 2 equations:

1. c + v = 40
2. 4c + 6v = 180

You can solve this system of equations three ways:

• Substitution Method
• Elimination Method
• Cramers Rule

No matter what method we choose, we get c = 30, v = 10.

Now let's check our work for both given equations for c = 30 and v = 10:

1. 30 + 10 = 40 <-- This checks out
2. 4c + 6v = 180 --> 4(30) + 6(10) --> 120 + 60 = 180 <-- This checks out