Answer :
So, here we have an exponential function.
Remember that an exponential function has the form:
[tex]y=a(b)^x=a(1\pm\frac{r}{100})^x[/tex]Where a represents an initial amount, and r is the rate of this amount to change. (Increase, or decrease).
So, given that the population of City A in 2000 was 40 thousand people and the population increased by 13% each year, we can say that
[tex]\begin{gathered} a=40 \\ b=1+\frac{13}{100}=1.13 \end{gathered}[/tex]So,
[tex]f(x)=40(1.13)^x[/tex]For city B:
[tex]\begin{gathered} a=40 \\ b=1+\frac{16}{100}=1.16 \\ g(x)=40(1.16)^x \end{gathered}[/tex]But something different happens with city C. This is not an exponential function, this is a linear function.
So,
[tex]h(x)=40+10x[/tex]