Calculate how many mL of the 5% w/v AgNO3* solution must be added to 0.4020g of the sample to precipitate all the chloride. Assume the sample is NaCl.

* this means tat there are 5 grams of silver nitrate present per 100ml of solution.

You don't have enough information. What about the 0.4020 gram sample? What is it? or what is percent Cl^- in it?