My lengthy analysis below...
The notation in (a) means that your electrodes consist of a silver electrode in a solution of
The other electrode is hydrogen gas bubbled over an inert platinum in an acidic solution (such as 1.0 M HCl). The standard potential is 0.00 V
The double vertical line represents the barrier between the two half-cells.
The hydrogen cell is the anode, so oxidation occurs
Together, the reaction is
In (b), we can start with two reduction half-reactions, and their potentials:
Both of these occur by passing the chemicals over an inert platinum electrode.
Since the second half-reaction has the greater potential, it is the reduction (and the cathode). The bromine process is the oxidation (and the anode).
So the half-reactions are
(We now know that the cell consists of one solution containing
Cell voltage 1.33 V - 1.06 V = 0.27 V