Atrain that is 80 meters long travels 240 meters in 6 seconds. how many seconds would it take the train to pass through a 480 meter long tunnel.

Speed=distance / time
Data:
distance=240 m
time=6 s

Speed of this train=240 m / 6 s=40 m/s

The train pass through 480 meters of tunnel, therefore the distance will be:
distance of the tunnel + distance of the train= 480 m + 80 m=560 m

speed=distance / time   ⇒  Time=distance / speed
Data:

distance=560 m
speed=40 m/s

Time=560 m/ (40 m/s)=14 s

14 seconds will take the train to pass through a 480 m long tunnel.