From the given information, the distance between the two cars will be 40+50 miles or 90 miles.
To get the time required for the two cars to be apart by 450 miles get the equation as,
time = Total distance travelled divided by the distance travelled in 1 hour
t=45090
t=5
As the time at the start of travelling was 5am, adding the time taken will be
5hours+5hours=10am.
Ans : The two cars will be apart from each other by 450miles at 10am.