a. 0.6 moles
b. 35.1 grams
Further explanation
Given
Volume = 0.2 L
Molarity = 3 M
Required
mol of Sodium chloride
Solution
Molarity shows the number of moles of solute in every 1 liter of solute or mmol in each ml of solution

Where
M = Molarity
n = Number of moles of solute
V = Volume of solution
Input the value :
n = M x V
n = 3 M x 0.2 L
n = 0.6 moles
Mass of NaCl :
= mol x molar mass of NaCl
= 0.6 x 58.5 g/mol
= 35.1 grams