if 4 grams sodium chloride dissolve in 200ml, whats the concentration of sodoum chloride in the water.?

Molar mass of NaCl = (23.0 + 35.5) g/mol = 58.5 g/mol
No. of moles of NaCl = (4 g) / (58.5 g/mol) = 0.0684 mol

Volume of solution = 200 mL = 0.2 L

Concentration of NaCl = (0.0684 mol) / (0.2 L) = 0.342 M