I drew a graph and plotted the coordinates. a hexagon is the shape u will get
The formula

, for n=1 becomes

.
Comparing

with

, we see that
P=900, and 1+r=1.185, which means that r=0.185.
r=0.185 can be written as 18.5%, as a percentage.
Answer: 18.5%
Kevin runs:
8 miles -- 84 minutes;
6 miles -- x minutes.
Write a proportion:

Then 
Answer: it takes him 63 minutes to run 6 miles