Question 900850
The question can be restated as, how much time does each brother travel until they are 200 miles apart?


RT=D, uniform rates rule for travel. 


The early slow brother travels for 1 hour longer than the fast late brother.
Let t = travel time for the fast late brother.



__________________speed___________time________distance
EarlySlow_________55______________t+1_________55(t+1)
LateFast__________70_______________t__________70t
TOTAL_________________________________________200


The main objective now is solve for t:
{{{highlight(55(t+1)+70t=200)}}}


Easily compute t+1 for the early, slow brother.