#### Answer

There were around $6.76$ million enrollments in 2006 and around $7.235$ million enrollments in 2010..
2010 is the midpoint of 2008 and 2012, the last two entries in the table.
Thus, the midpoint of the last two entries is:
$=\left(\frac{2008+2012}{2}, \frac{6.97+7.50}{2}\right)
\\=\left(\frac{4020}{2}, \frac{14.47}{2}\right)
\\=(2010, 7.235)$
There were around $7.235$ million enrollments in 2010.

#### Work Step by Step

The coordinates of the midpoint the points $(x_1, y_1)$ and $(x_2, y_2)$ is given by the formula:
$$=\left(\dfrac{x_1+x_2}{2}, \frac{y_1+y_2}{2}\right)$$
2006 is the midpoint of 2004 and 2008, the first two entries in the table.
Thus, the midpoint of the first two entries is:
$=\left(\frac{2004+2008}{2}, \frac{6.55+6.97}{2}\right)
\\=\left(\frac{4012}{2}, \frac{13.52}{2}\right)
\\=(2006, 6.76)$
There were around $6.76$ million enrollments in 2006.
2010 is the midpoint of 2008 and 2012, the last two entries in the table.
Thus, the midpoint of the last two entries is:
$=\left(\frac{2008+2012}{2}, \frac{6.97+7.50}{2}\right)
\\=\left(\frac{4020}{2}, \frac{14.47}{2}\right)
\\=(2010, 7.235)$
There were around $7.235$ million enrollments in 2010.