Given below are aqueous solutions of strong electrolytes. For each solution, specify the concentration of each ion

0.15 M NH4NO3 (aq)
0.120M Mg(NO3)2(aq)

What's your problem with this? The first one is 0.15M in NH4NO3. There is 1 NH4^+ and 1 NO3^- ion in NH4NO3 so (NH4^+) = 0.15M and (NO3^-) is 0.15M