Given that the standard potentials $\left(E^0\right)$ of $C{u}^{2+}/Cu$ and $C{u}^{+}/Cu$ are 0.34 V and 0.522V respectively, the $E^0$ of $C{u}^{2+}/C{u}^{+}$ is:

$\begin{array}{l}C{u}^{2+}+2e^{-}\to Cu,\Delta G_1^0=-2F\left(0.34\right)\mathrm{......}\left(i\right)\\ C{u}^{+}+e^{-}\to Cu,\Delta G_2^0=-F\left(0.522\right)\mathrm{......}\left(ii\right)\end{array}$

Subtract (ii) from (i)

$\begin{array}{l}C{u}^{2+}+e^{-}\to C{u}^{+},\Delta G_3^0=-F\left(E^0\right)\\ \therefore \Delta G_1^0-\Delta G_2^0=\Delta G_3^0\\ \Rightarrow -F{E}^0=-2F\left(0.34\right)+F\left(0.522\right)\\ \Rightarrow E^0=0.68-0.522=0.158V\end{array}$