We see from the balanced equation that there is only 1 mole to 1 mole ratio.
Calculate moles of AgNO3:
moles AgNO3 = 0.2503 M * 0.02022 L = 0.00506 mol
This is equal to moles of NaCl,
moles NaCl = 0.00506 mol
So the concentration is:
Concentration = 0.00506 mol / 0.015 L = 0.3374 M