#### Answer

By the year 2015.

#### Work Step by Step

Consider the provided condition. It shows that the average increase in the percentage is 2.4 each year and the initial percentage is 31%. So, for 67% the provided condition can be formulated as,
$31+2.4x=67$
Here, x shows the number of years after the year 2000.
Now, solve the above equation.
$\begin{align}
& 31+2.4x=67 \\
& 2.4x=67-31 \\
& x=\frac{36}{2.4} \\
& =15
\end{align}$
The above equation has x as the number of year after the year 2000. So the year in which the percentage will be 67% is,
$2000+15=2015$
Thus, 67% of all American adults will view a college education as essential for success by the year 2015.