If 45.0 grams of solute was dissolved to produce a 30.0 % by mass solution, determine the mass of the solvent alone.

105 grams.

Explanation:

If 45.0 grams of solute is 30.0% of the solution, you would set up an equation like this.

0.3x = 45.0 (x being the total mass of the solution).

When this is solved for, the total mass of the solution is found to be 150.

Since the problem is asking for the mass of the solvent alone, you need to subtract 45 grams (the mass of the solute) from 150 grams (the mass of the entire solution) to give you 105 grams, the mass of just the solvent.