Question 711746
The situation about the two cars is already somewhat simplified becuase the rate at which they are separating is the difference between their speeds.  The both left the starting point at the same time.  


The rate by which they are separating from each other is 70-30 miles per hour.
{{{70-30=40}}}.


{{{40*m=30}}}, for m being the time when the distance is 30 miles,
{{{m=30/40}}} or 45 minutes.