Answer:

Step-by-step explanation:
As we know by the theory of flux that if charge "q" is enclosed in a closed surface then total flux through the surface is given as

so here total flux passing through the cube is given as

now we will have

now as we know that charge is placed at the center of the cube
so the total flux is uniformly passing through all faces of the cube
so flux passing one side of the cube is given as

