[MsGail]

If I am given a specific volume and molarity, how I do I go about describing how to make the complex salt solution?

For example: I want to make a 100mL soln of 10mM NaCl and 5mM dibasic sodium phosphate

[Borek]

If I am given a specific volume and molarity, how I do I go about describing how to make the complex salt solution?

For example: I want to make a 100mL soln of 10mM NaCl and 5mM dibasic sodium phosphate

Calculate for every salt separately, just don't forget to dissolve everything in some smaller amount of water and dilute to the final volume.