Answer:
28 dvds in 14 weeks
Step-by-step explanation:
4 dvds in two weeks
2 dvds in a week
14 weeks equal 28 dvds
10C4 represent the Combinations of 10 objects taken 4 at a time.
The formula for nCr is:

In the given case, n=10 and r=4. Using these values we get:

This means we can make 210 combinations of 10 objects taken 4 at a time.
Let's start by understanding that the graph is a linear line. We have a common difference if 4.5 for every 10x we have more.
We can start by finding the gradient, using rise over run. Let's take (10, 4.5) and (20, 9)
Our rise is 9 - 4.5 = 4.5 and our run is 10. Then, our gradient becomes 4.5/10 = 0.45
Now, we can substitute points using the point-slope form.
y - 4.5 = 0.45(x - 10)
y - 4.5 = 0.45x - 4.5
Hence, our line becomes y = 0.45x and you can verify by substituting in points from the table.