Help with Textbook problem G.21

[Ellen Amico 2L]

The question is: "A solution is prepared by dissolving 0.500 g of KCl, 0.500 g of K2S, and 0.500 g of K3PO4 in 500. mL of water. What is the concentration in the final solution of (a) potassium ions; (b) sulfide ions?"
I calculated the molarity of the solution, but how do I find the concentration of the individual ions?

[LNgo 1G]

You can use the mole ratios of the individual ions to the compounds given to find the moles of each ion in the solution and divide by volume to get the concentration from there.

[Lauren Tanaka 1A]

To find the concentration of the individual ions you take the moles of each compound and multiply it by the mole ratio of the ions in that compound. This will leave you with the number of moles of the particular ion. From there you are able to use the molarity equation c = n/v (where n is the calculated moles of the particular ion and v is the volume given). Plug those numbers in and you should end up with the concentration of the particular ions.