Acar starts 45km (w) of a railroad crossing and travels to 15km (e) of the railroad in 1.2h. what is the velocity of the car in meters per second.

If the car starts at a point that's 45 km West of a place, and goes
to a point that's 15 km East of the same place, then the car had to
drive  (45km + 15km) = 60 km all together.

                       Speed = (distance covered) / (time to cover the distance)

                                   =  (60 km)  /  (1.2 hours)

                                   =        50  km/hour  .

But the question wants the answer in a different unit,
so we  ( I )  have to convert it.

1 km = 1,000 meters
1 hour = 3,600 seconds

     Car's speed  =  (50 km/hr) x (1000 m/km) x (1 hr/3600 sec)

                             =         (50 · 1000 / 3600)  m/sec

                             =              13.89  m/s        (rounded)

That's still not the velocity of the car.
Its velocity is

                                             13.89 m/s  to the East

The objects are acted upon by only one force. gravity. mass times the acceleration of gravity (-9.81meters/second squared).