Answer:
They will meet in 1.8 hours.
Step-by-step explanation:
Given that, distance between trains = 306 miles
Let they take time
to meet each other.
Speed of first train = 90 mph
Speed of second train = 80 mph
Let distance traveled by first train =
miles
Formula for distance:

Distance traveled by first train, 
Let distance traveled by first train =
miles
Formula for distance:

Distance traveled by first train, 
Total distance traveled is 306 miles.
i.e.

They will meet in 1.8 hours.