Go on then work out the the Na/K ratio.

It is quite simple really.

First, determine the amount of mol's of Cl.

You know that (simplified):

NaCl + KCl -> AgCl

In other words, all Cl is used by the Silver.

So you have.

4.626 g - X g NaCl +

X g KCl = mols Cl = mols AgCl

58.443g/mol 74.551 g/mol

Once you solve for X you know the amount (in grams) of NaCl (4.626 - X) and KCl (X) in the original mixture, so the ratio is pretty easy from that point on.