[avnis]

Given the following half-reactions:
 Ce4+ + e− → Ce3+      E° = 1.72 V 
 Fe3+ + e− → Fe2+      E° = 0.771 V 
A solution is prepared by mixing 7.0 mL of 0.30 M Fe2+ with 5.0 mL of 0.11 M Ce4+.

What is the potential of a platinum electrode dipped into the resulting, equilibrated, solution (relative to SHE)?

so i know that it is not just (1.72 - 0.771),

i did the ice table but it of no use couldn't figure it out. give me any ideas.
initial species in solution in moles Fe2+ = 0.0021 moles Ce4+= 0.00055,Fe3+ = 0 Ce 3+ = 0

[BluePill]

Write the net ionic equation so you would know the stoichiometric factors. Then, use the Nernst equation.

E_cell = E^o_cell - [(RT/nF)*ln(K)]

where: K is the equilibrium constant and  E^o_cell = E^o_cathode - E^o_anode