The population of a suburb of Cincinnati has shown a linear growth in the years 1991-2006. The population in 1991 was 21400 people and it has been growing at a rate of 625 people per year.

Let t be the number of years after 1991, since the population has been growing at a rate of 625 people per year and the population in 1991 was 21400 people, then we can set the following equation:
[tex]P=21400+625t\text{.}[/tex]Now, if this behavior continues, then the population in 2008 will be:
[tex]P=21400+625\cdot(2008-1991_{})\text{.}[/tex]Simplifying the above equation we get:
[tex]\begin{gathered} P=21400+625\cdot17, \\ P=21400+10625, \\ P=32025. \end{gathered}[/tex]Answer:
(a)
[tex]P=21400+625t\text{.}[/tex](b)
[tex]32025.[/tex]