Question 362228
If they have constant velocities in the initial condition:
Let's say v1 = speed of faster truck and v2 = speed of slower truck..
The distance they travel in a certain time is X = V*t where t is the time.
Let's say x1 = distance of faster truck from warehouse and x2 = distance of slower truck from warehouse..

So that >> x1 = v1*t and x2 = v2*t

Total distance after 5 hours is 

x1 + x2 = v1*5 + v2*5 = 600 miles (1)

We know that v1 = v2 + 5 (2)

And therefore, put v1 in the (2)nd equation into the (1)st equation such that;

(v2 + 5)*5 + v2*5 = 600  >>

5*v2 + 25 + 5*v2 = 600   >>

10*v2 = 575 miles     >>

v2 = 57.5 miles per hour and if you put v2 into any equation you'll get >>

v1 = 62.5 miles per hour

RF.