$E_{1}^{0}=0.15 V, \Delta G_{1}^{0}=-n_{1} E_{1}^{0} F$

$\frac{ C u^{+}+e^{-} \rightarrow C u, E_2^0=0.50 V, \Delta G_{2}^{0}=-n_{2} E_{2} P}{C u^{2+}+2 e^{-} \rightarrow C u, E^{0}=7, \Delta G^{0}=-n E^{0} F}$

$\Delta G^{0}=\Delta G_{1}^{0}+\Delta G_{2}^{0}$

$-n E^{0} F=-n_{1} E_{1}^{0} F-n_{2} E_{2}^{0} F$

or $-2 E^{0} F=-1 F \times 0.15+(-1 F \times 0.50)$

or $-2 E^{0} F=-0.15 F-0.50 F$

or $-2 F E^{0}=-F(0.15+0.50)$

$\therefore \quad E^{0}=\frac{0.65}{2}=0.325 V$