[tex]N(t)=\dfrac{54}{0.35+0.68^t}[/tex]
The number of beavers initially introduced is the population at time [tex]t=0[/tex], so you need to find [tex]N(0)[/tex].
[tex]N(0)=\dfrac{54}{0.35+0.68^0}=\dfrac{54}{1.35}=40[/tex]
The number of beavers after 5 years is given by [tex]N(5)[/tex].
[tex]N(5)=\dfrac{54}{0.35+0.68^5}\approx\dfrac{54}{0.495}\approx109[/tex]
The change in the beaver population between [tex]t=5[/tex] and [tex]t=10[/tex] is simply the difference [tex]N(10)-N(5)[/tex]. Evaluate the function at these points (you already know [tex]N(5)[/tex]) and subtract. You should get approximately [tex]36.49\approx36[/tex].
