Question 5493
Use the formula 
rate*time=distance
Let x = the slower train
x+6 = the rate of the faster train
when traveling at the same time toward each other, add their rates together:
x+x+6 or 2x+6
then
r*t=d
(2x+6)*5hours=450miles
10x+30=450
10x=420
x=42
the slower train is traveling at 42mph
the faster train is traveling 6 miles faster at 48 mph.

check the answer by the time...
the 42mph train travels 5 hours or 210 miles
the 48mph train travels 5 hours or 240 miles
210miles + 240 miles = 450 miles
so this is correct.