Answer: after 1.8 hours, they would be 306 miles apart.
Explanation:
Let t represent the time it will take for the two trains to be 306 miles apart. It means that after t hour, both trains would have covered a total of 306 miles.
Distance = speed × time
The eastbound train travels at 75 miles per hour. It means that the distance travelled by the eastbound train after t hours is 75t miles.
The westbound train travels at 95 miles per hour. It means that the distance travelled by the westbound train after t hours is 95t miles.
Since the total distance covered after t hours is 306 miles, it means that
75t + 95t = 306
170t = 306
t = 306/170
t = 1.8