Figure shows three spherical and equipotential surfaces $A,B$ and $C$ round a point charge $q$. potential difference $V_A-V_B=V_B-V_C$. If $t_1$ and $t_2$ be the distances between them, then

Potential difference between two equipotential  $A$ and $B$,

$V_A-V_B=kq\left(\frac{1}{r_A}-\frac{1}{r_B}\right)$

$=kq\left(\frac{r_B-r_A}{r_A{r}_B}\right)=\frac{kq{t}_1}{r_A{r}_B}$

or $t_1=\frac{\left(V_A-V_B\right)r_A{r}_B}{kq}$

or $t_1 \propto r_A{r}_B$ 

Similarly, $t_2=r_B{r}_C$

Since, $r_A<r_B<r_C$, therefore, $r_A$

$\therefore t_1<t_2$