* Calculate the mass of the solid: Since 0.2 represents the fraction of the solid that dissolves, we need to figure out what the total mass of the solid was. We don't have that information, so we can't determine the exact mass of the solution.

* Understand the concept: The mass of the solution is simply the sum of the mass of the solvent and the mass of the solute (the dissolved solid).

Example:

Let's assume the original mass of the solid was 1 gram.

* Mass of solid dissolved: 0.2 * 1 gram = 0.2 grams

* Mass of solution: 0.2 grams (solid) + 100 grams (solvent) = 100.2 grams

In Conclusion:

You need to know the original mass of the solid to calculate the exact mass of the solution. The formula is:

Mass of solution = Mass of solvent + Mass of solute