Physics Help?

I just don't get it...

1. A man drops a stone into a water well on
his farm. He hears the sound of the splash
3.86 s later.
How deep is the well? The acceleration due
to gravity is 9.8 m/s
2
and the speed of sound
in air is 324 m/s.
Answer in units of m.

2.
A speedy tortoise can run at 0.1 m/s, and a
hare can run 17 times as fast. In a race, they
start at the same time, but the hare stops to
rest for 2.1 min, so the tortoise wins by a shell
(20 cm).
How long does the race take?
Answer in units of s.

Also, What is the length of the race?
Answer in units of m