Velocity is speed+direction (the speed of something in a given direction). We know that running on a track, one is moving forwards, which is why the velocity given as positive. Now we do some simple algebra. 120 minutes is equal to 2 hours. At a velocity of 4 miles an hour, for 2 hours, you multiply 4x2 and get 8, which is how far (in miles, units are important) the man has traveled once he comes to a stop.
If there is a change in the gene, this can further create a new generation of organisms with this change. With certain changes, it enables organisms to survive in other conditions.
