The average speed of car 1 = 45 mph.
the average speed of car 2 = 65 mph.
time elapsed between the start of car 1 and start of car 2 = 18 minutes.
how long before car 2 overtakes car 1? hour.

Step-by-step explanation:

18 min = 0.3 h

Car 1 started 0.3 h before Car 2.

  Let t = time of Car 2. Then

t + 0.3 = time of Car 1

Distance = speed × time, and both cars travel the same distance. Then

Check:

OK.

Car2 overtakes Car1 after 0.675 hours

Step-by-step explanation:

To solve this question, we must know that

Speed = distance / time

Speed_car1 = 45 mph = distance_car1/ time_1

Speed_car2= 65 mph = distance_car2/ time_2

We know that

time1 - time2 = 18 minutes = 0.3 h

And, at the time of the overtake, both cars will have traveled the same distance.

So,

distance_car1 = 45 mph * time1 = distance_car2 = 65 mph * time2

time1 / time2 = 65/45

time1 = 1.444*time2

Then,

1.444*time2- time2 =  0.3 h

time2 = 0.675 h

time1 = 0.975 h

Car2 overtakes Car1 after 0.675 hours

step-by-step explanation: