A mixture is a physical combination of two or more substances that are not chemically combined. A solution is a homogeneous mixture of two or more substances in which the solute is uniformly distributed throughout the solvent.

In a cup of salt and water, the salt and water are not chemically combined, so the mixture is not a compound. The solute (salt) is uniformly distributed throughout the solvent (water), so the mixture is a solution.

Therefore, a cup of salt and water can be both a mixture and a solution.