Question 886341
Let A = rate for car departing A
Let B = rate for car departing B


_______________________rate________time________distance
Same direction_________A-B__________7___________70
towards-opposite_______A+B__________1___________70


Understand that data table before continuing.  Really we do not know if A or B is the larger (positive) speed.  We have nothing to distinguish car A from car B.  


Now, based on uniform rates for Travel, we have two equations based on RT=D rate time distance.



_______________________rate________time________distance___Equations
Same direction_________A-B__________7___________70________{{{highlight((A-B)*7=70)}}}
towards-opposite_______A+B__________1___________70________{{{highlight((A+B)*1=7)}}}


Two equations in two unknowns; Solve for A and B.