Answer:
16.7 %(m/m)
Step-by-step explanation:
The percent by mass of a solution (% m/m) is defined as 100 times the ratio of the mass of solute (The substance in the lower amount, NaCl) and the mass of the solution = Mass solute + Mass Solvent (water).
Mass Solution:
100g NaCl + 500g water = 600g solution
Mass Percent:
100g NaCl / 600g solution * 100
= 16.7 %(m/m)