When car 2 leaves at 6:30, 1 hour after Car 1, Car 1 is 35 miles from Car 2. They then are separating at the rate of 35mph+45mph or 80mph, so after 3 hours, at 9:30 they will have separated an additional 3×80 = 240 miles. So they will be 35+240 or 275 miles apart at 9:30. Edwin