The net cell reaction for the iron-silver voltaic cell would be:
3Ag+ + Fe --------> 3Ag + Fe3+
wherein it comes from the reaction of the cathode and the anode:
Ag+ + e- -------> Ag, for the cathode and;
Fe -------> Fe3+ + 3e-, for the anode
When both equations would be multiplied, the it would now yield the balanced net reaction as stated above.