# $E^o\large\frac{A^{+3}}{A^+}$$=xV,E^o\large\frac{A^{+3}}{A^{+2}}$$=yV,E\large\frac{A^{+2}}{A^+}=$?

$\begin{array}{1 1}(a)\;2x-y&(b)\;x\\(c)\;y&(d)\;x-y\end{array}$

$A^{+3}+2e^-\rightarrow A^+\qquad E^o=x;\Delta G_1$
$A^{+3}+e^-\rightarrow A^{+2}\qquad E^o=y;\Delta G_2$
$A^{+2}+e^-\rightarrow A^+\qquad E^o=?;\Delta G_3$
$\Delta G_3=\Delta G_1-\Delta G_2$
$\eta FE^o=-2Fx+1Fy$
$E^o_{A^{+2}/A^+}=2x-y$
Hence (a) is the correct answer.