I do not know how I should approach this problem either.
The following electrochemial cell has a potential of+0.617V at 25 degrees Celsius
Pt ! H2(g,1.00atm) ! H^+(aq,1.00M) !! Ag^+(aq) ! Ag
The standard reduction potential ,E naught of Ag^+ = 0.700V. What is the Ag^+ concentration?
If the Ag^+ were at the standard state of 1.0 M, then Ecell would have been 0.700 v.
It isn't, so
Ehalf cell = Eo-(0.0592/n)log(red/ox)
Ehalf cell is 0.617, Eo = 0.700, n is 1 for the number of electrons, the reduced form is Ag so that is 1 in the standard state (solid), and the oxidized form is x. Solve for x.