Final answer:
The question involves finding the mass of a dissolved solid in a water sample, which pertains to solution concentration in chemistry.
Step-by-step explanation:
The student's question relates to the calculation of the mass of a dissolved solid in water and is a typical chemistry problem concerning solution concentration. To determine the mass of the dissolved solid, the student needs to subtract the mass of the solute from the total mass of the solution.
This process is similar to the one where you would subtract the mass of NaCl from the total mass to find the mass of water needed to make a solution. The formula for the calculation is mass of solution = mass of solute + mass solvent. Given that the mass of the dissolved solid (solute) is 3.9 g and the mass of the water sample (solvent) is 24.5 g, the total mass of the solution would be the sum of the two.