Answer:
200 CDs
Explanations:
In the year 1970, 350 CDs were sold
In the year 1985, 275 CDs were sold
If x represents the year, and y represents the number of CDs sold
Note that the duration between 1900 and 2000 is 100
This means that 1970 is equivalent to 70 years, 1985 is equivalent to 85 years, and 2000 is equaivalent to 100 years
The point (70, 350) represents 350 CDs sold in 1970
The point (85, 275) represents 275 CDs sold in 1985
Using the equation of the line:
y - y₁ = m(x - x₁)
where m is the slope of the line
m = (y₂ - y₁) / (x₂ - x₁)
m = (275-350) / (85-70)
m = -75/15
m = -5
The equation of the line then becomes:
y - 350 = -5 ( x - 70)
y - 350 = -5x + 350
y = -5x + 350 + 350
y = -5x + 700
To know the number of CDs sold in 2000, since 2000 is equivalent to 100 based on the duration from 1900 to 2000
substitute x = 100 into the equation y = -5x + 700
y = -5(100) + 700
y = -500 + 700
y = 200
200 CDs were sold in year 2000