a silver coin has a mass of 2.50g and is analysed for silver by dissolving in dilute nitric acid, and precipitating silver as solid AgCl and weighing this. if the percipitat weighs 2.99g what percentage of silver is the coin?

2.99 g AgCl x (atomic mass Ag/molar mass AgCl) = about 2.25g Ag but you need to confirm that.

Then % Ag =(mass Ag/mass sample)*100 = ?
Approx 90%; BUT that must be an old dime. The new ones don't have that much.