Answer
See below
Work Step by Step
The Lotka-Volterra equations to model populations were food-fish is $F$ and sharks are $S$ is...
$\frac{dF}{dt}=kF-aFS$ and $\frac{dS}{dt}=-rS+bFS$
b) In the absence of sharks, ample food supply would support the exponential growth of the fish population were $dF/dt = kF$, where k is constant and positive. In the absence of fish, we assume that the shark population would decline at a rate proportional to itself that is $dF/dt =-rS$, where r is a positive constant.
