.
This formulation includes tons of data and words that are not relevant to the solution.
They, probably, were specially placed into the formulation to confuse the reader.
I filtered out all unnecessary words and data, and below is my dry remainder to solve.
A motor barge traveled 100 miles downstream at a speed of 10 miles per hour.
The rate of the current is 3 miles per hour.
How much longer will it take for the barge to return back than to travel downstream ?
Now I am ready to solve.
Since the barge speed downstream is 10 mph, its speed in still water is 10-3 = 7 mph.
Since the barge speed in still water is 7 mph, its speed upstream (relative to the river's banks) is 7-3 = 4 mph.
Time downstream is = 10 hours.
Time upstream is = 25 hours.
The difference is 25 - 10 = 15 hours.
ANSWER. How much longer ? - 15 hours longer.