How deep is the well?

S = $\frac{1}{2} \times g \times t^{2}$ = $327 \times (2.08-t)$

We get t = 2.02

So S = $\frac{1}{2} \times g \times t^{2}$ = $\frac{1}{2} \times 9.8 \times 2.02^{2}$ = 20

First we need to write the equation for the time

$t_1 + t_2 = 2.08$ second

Where $t_1$ is equal to the time it takes for the stone to hit the bottom of the well and $t_2$ is equal to the time it takes for the sound to travel to Jill's ear.

From that we can use the equation

$s = V_o \times t + \frac {1}{2} \times g \times t^2$ to solve $t$

In which

$t_1$ will be equal to $\sqrt {\frac {2s}{g}}$

And $t_2$ will be equal to $\frac {s}{v}$

Finally we get

$\sqrt {\frac {2s}{g}} + \frac {s}{v} = 2.08$ second

Using algreba we find the answer = 20 meter