#### Answer

$p(t)=175+2.5t$ (in thousands of people), where $p(t)$ is the population of the country and $t$ is the amount of years since $2008$.

#### Work Step by Step

In the equation $p(t)=at+b$:
The rate of change (in population), $a$, is $2,500$ people every year.
The initial output, $b$, is $175,000$ people.
Rewrite this as $p(t)=2,500t+175,000$, or simplify it to $p(t)=2.5t+175$ (in thousands of people).