Given:
There are given that the Appalachain trail planned to increase the distance covered by 20%.
Step-by-step explanation:
(a):
According to the question:
We need to find the number of miles did the hiker travel on the first.
So,
To find the number of miles, we use the below equation:

Then,

Hence, he started with 4 miles.
Part B:
According to the question:
There are given 7 days.
So,
We get the second part of the equation because each day is increased by 20%.
So, we have:

So,
Our top half will be x multiplied by:

Because it is the 7th day and we are increasing by:

So,
The equation is shown below:

Part C:
We now have x which is 4.
So,
We plug x into the equation above and remove the 51.664.
Then,
We also change the expression:

Because it's the 10th day, not the 7th.
So,
Our equation now looks like this:

Hence, the total number of miles the hiker will travel in 10 days is 103.83.