The mass/volume percent of a sodium sulfate and water solution is 12.0% m/v. If the density of the solution 1.22 g/mL, what is the molarity of the solution?
12% m/v (w/v) means 12g solute/100 mL solution.
How many mols is 12 g Na2SO4? That's mols = grams/molar mass = approx 0.08 but you need a more accurate answer than that.
What volume? That's 100 mL or 0.1L
M = mols/L. I don't think the density is needed.