The question is from RC Mukherjee:

To determine the Nacl content in commercial NaOH, 2g of latter was dissolved in water and an excess amount of an AgNO3 solution was added to the solution. The precipitate formed was washed and dried. Its mass was 0.287g. Find the mass of NaCl in the initial sample.

The Question itself is erroneous. One should NOT add AgNO3 to the NaOH solution as apart from the AgCl, AgOH and Ag2O shall ALSO precipitate. The 0.287 g ppt, thus shall be a mixture of these three componants, out of which how much is AgCl, one can not find out.

Before adding the AgNO3, therefore, the NaOH should be neutralized with HNO3, and then only the ppt shall be of AgCl from which one can then calculate the amount of NaCl in the sample.