The displacement of a car that travels 20 km west and then 5 km east is 5 km west. Displacement is a measure of the change in position of an object, and it is calculated by taking the final position of the object and subtracting its initial position. In this case, the car starts at an initial position and travels 20 km west, so its final position is 20 km west of its starting point. Then, the car travels 5 km east, which brings it back to its starting point. Therefore, the displacement of the car is 5 km west, as it has moved 5 km west of its starting point during its journey.