Solubility,,,,,add water to the mixture,salt will dissolve to form a solution while sand is insoluble,,,,,decant the salt solution as filtrate and remain with sand as residue,,,,,if salt crystals are needed,,,,evaporate the filtrate to dryness.
Dissolve the mixture of sand and salt in water, make sure all salt is dissolved. Filtrate the solution a couple of times and use vacuum filtration at the end to obtain a clear solution. At this point you will have wet sand and a salty solution. Take the salty solution and evaporate water to obtain the salt.
No it will not be passed on. As the question states the moths live in a green forest so the green moths have camouflage, which is a big advantage. But the orange moth doesn’t and will very easily be spotted by predators(will die very soon probably before reaching its reproductive period) thus the mutation wont be passed on.
To balance a reaction, the amount of reactants must be equal to the amount of products, as stated by the Law of Conservation of Matter. It may help you to keep track of the number of each element in a list as you try to balance. It's not able to be balanced.