Question

write the methods you will use to separate a mixture of iron-fillings,common salt and sand

Answer 1

First, take all the things in a beaker, By magnetic separation,i.e., using a magnet we can separate the iron fillings from the mixture.
Then, mix the dissolve the remaining mixture in water. The salt will dissolve, whereas, the sand can be filtered out. Then, evaporate or crystallize to get the salt. 

Thus, we used: Magnetic separation, Dissolution then filtration and then crystallization/Evaporation.

Answer 2

use magnet to separate iron fillings.and put the salt and sand in water . let the salt dissolve in water and now filter the solution. now sand is also separated from the mixture. now heat the salt solution . the water in the solution gets evaporated and the salt will remain. thus the mixture of common salt ,iron fillings and sand are separated.