Answer
$V=-8.9KV$
Work Step by Step
The total potential on the surface of sphere 2 is
$V=V_1+V_2$
$V=K\frac{q_1}{r_1}+K\frac{q_2}{r_2}$
We plug in the known values to obtain:
$V=9\times 10^9(\frac{1\times 10^{-8}}{2-0.03})+9\times 10^9(\frac{-3\times 10^{-8}}{0.03})$
$V=-8.9KV$
