Verified Answer :

\(S=6a^{2} \\ \\ 6a^{2}=864 \\ \\ a^{2}=144\)

naǫ

A cube has six identical faces, so the surface area is six times the area of one face.

Let x be the area of one face.
\(6x=864 \\ x=\frac{864}{4} \\ x=144\)

The area of one face of this cube is 144 in².