Answer
Enrollment in 2002 was about 6.25 million.
Enrollment in 2006 was about 6.76 million.
Work Step by Step
To find the midpoint between points $(x_1,y_1)$ and $(x_2,y_2)$, we use the midpoint formula:
$\displaystyle Midpoint=(\frac{x_1+x_2}{2},\frac{y_1+y_2}{2})$
To estimate enrollment in 2002, we find the midpoint between $(2000,5.95)$ and $(2004,6.55)$:
$Midpoint=(\frac{2000+2004}{2},\frac{5.95+6.55}{2})$
$=(2002,6.25)$
Thus enrollment in 2002 must have been around 6.25 million.
Similarly, we estimate enrollment in 2006:
$Midpoint=(\frac{2004+2008}{2},\frac{6.55+6.97}{2})$
$=(2006,6.76)$
Thus enrollment in 2006 was around 6.76 million.
