Answer:
40 mph and 68 mph
Explanation:
Let x mph be the speed of the slower car, then 2x-12 mph is the speed of the faster car.
In 6 hours the faster car got to San Diego, so it travels the distance

By that time the slower car was 168 miles away from the destination, so the slower car travels the distance

It takes the slower car 6 hours to travel 12x-240 miles, so

Now,
