Pure water.
A salt solution contains impurities whereas pure water will not contain any impurities.
Impurities increase the boiling point (freezing point) of a substance.
Thus, I would expect the pure water solution to freeze faster than the salt solution.
Answer:
Apply Newton's second law in the moving direction.
Explanation:

Friction force applies in the opposite direction of motion; as a restriction.
Answer:
the displacement of the object is 5 units
Explanation:
The computation of the displacement of the object is shown below:
= Move to the right + move to the right - move to the left
= 6 units + 3 units - 4 units
= 9 units - 4 units
= 5 units
Hence, the displacement of the object is 5 units