Charge is symmetric to all faces of the cube, hence by symmetry each face would have equal flux passing though it.
Consider that the charge q is at a distance of 5cm from the square ABCD of each side 10 cm [figure]. The square ABCD can be considered as one of the six faces of a cube of each side 10cm. Then, according to Gauss’s theorem, total electric flux through all the six faces of the cube
Obviously, the flux through the square ABCD will be