A mixture of salt, sand, oil and water can be separated by using these steps-
i) Decantation- Oil floats on water (oil is insoluble in water), so it can be decanted easily.
ii) Filtration- The mixture is filtered easily, and sand is separated from the water (as it is insoluble in water), and only salt solution will be left.
iii) Evaporation- The water in the salt solution can be evaporated, and by this, the salt can be separated out.