This is an incomplete question, the complete question is attached below.
Answer : The coefficient of silver in the final, balanced equation for this reaction is, 3
Explanation :
Redox reaction or Oxidation-reduction reaction : It is defined as the reaction in which the oxidation and reduction reaction takes place simultaneously.
Oxidation reaction : It is defined as the reaction in which a substance looses its electrons. In this, oxidation state of an element increases. Or we can say that in oxidation, the loss of electrons takes place.
Reduction reaction : It is defined as the reaction in which a substance gains electrons. In this, oxidation state of an element decreases. Or we can say that in reduction, the gain of electrons takes place.
The given redox reaction is,
The oxidation-reduction half reaction will be :
Oxidation : 
Reduction : 
In order to balance the electrons, we multiply the reduction reaction by 3 and then added both equation, we get the balanced redox reaction.
The balanced redox reaction will be,
From the balanced redox reaction we conclude that, the coefficient of silver in the final balanced equation for this reaction is 3.
Hence, the correct option is 3.
