If the trains do not stop anywhere...
They will travel x hours...
One of them will move west at 45 mph and will be 45x miles from Spring west,
The other will move east at 54 mph and will be 54x miles from Spring east,
One - Spring - Other .... 792 miles
45x + 54x = 792 miles
99x =792,
x=792/99
x = 8 hours.
The two trains will be 792 miles apart in 8 hours.
