Question

If a car is traveling eastward, can its acceleration be westward?

Answer 1

Yes it can. It may be a bit counterintuitive but if the car is slowing down, even if it's traveling east, its acceleration is toward the west because it's decelerating and slowing down.

Answer 2

The motions moving in opposite directions cancel each other when they have the same magnitude or speed in this case. If the car travels towards east, then it can be possible that the acceleration goes west as this case points to deceleration. The acceleration then has a negative sign.