Answer
$$y = \frac{{80}}{{1 + 9{e^{ - t}}}}$$
Work Step by Step
$$\eqalign{
& \frac{{dy}}{{dt}} = y\left( {1 - \frac{y}{{80}}} \right),{\text{ }}\left( {0,8} \right) \cr
& {\text{The differential equation is in the form }}\frac{{dy}}{{dt}} = ky\left( {1 - \frac{y}{L}} \right) \cr
& \underbrace {\frac{{dy}}{{dt}} = y\left( {1 - \frac{y}{{80}}} \right)}_{\frac{{dy}}{{dt}} = ky\left( {1 - \frac{y}{L}} \right)} \to k = 1,{\text{ }}L = 80 \cr
& {\text{The general solution is }}y = \frac{L}{{1 + b{e^{ - kt}}}}{\text{ }}\left( {{\text{Example 6, page 419}}} \right) \cr
& {\text{Therefore, substituting }}k = 1{\text{ and }}L = 80 \cr
& \underbrace {y = \frac{L}{{1 + b{e^{ - kt}}}}}_ \downarrow \cr
& y = \frac{{80}}{{1 + b{e^{ - t}}}}{\text{ }}\left( {\bf{1}} \right) \cr
& {\text{Using the initial condition }}\left( {0,8} \right) \cr
& 8 = \frac{{80}}{{1 + b{e^0}}} \cr
& b = 9 \cr
& {\text{Substituting }}b{\text{ into }}\left( {\bf{1}} \right) \cr
& y = \frac{{80}}{{1 + 9{e^{ - t}}}} \cr} $$
