Solution:
Given that the population model growth of Pleasantburg is expressed as

Suppose that the population t years after January 1, 2012 is expressed as

This implies that at the first year (January 1, 2012), t equals zero.
To solve for the population of Pleasentburg, we determine the value of t between January 1, 2012 and January 1, 2021.
The number of years between the two periods is 9 years.
Thus, substitute the value of 9 for into equation 2.
This gives

Hence, the population of Pleasantburg on January 1, 2021 is 23127 (nearest person).