Answer:
10 minutes 20 seconds
Explanation:
It is given that the flat head rail tunnel in Montana is about 
 miles long.
 miles long.
Length of rail tunnel = 

A train travels at a speed of 3/4 miles per minute.
 miles
 miles
The formula for time is





Therefore, the time taken by the train to go through the tunnel is 10 minutes 20 seconds.