Electric charges occupy a small volume. The electric flux through a...

According to Gauss's law, the total electric flux through a closed surface is given by $\Phi = \dfrac{q_{\text{enclosed}}}{\varepsilon_0}$.

The flux depends only on the total charge enclosed by the surface and is independent of the size or shape of the closed surface.

Since the entire charge is enclosed by both the $10 \text{ cm}$ and $20 \text{ cm}$ spheres, the enclosed charge remains the same.

Therefore, the electric flux through the $20 \text{ cm}$ sphere will be the same as that through the $10 \text{ cm}$ sphere, which is $25 \text{ V m}$.