Let the edge of a square be x and sum of its edges =12x

Now, by condition, \( \Large x^{3} = 12x \) [Because, x ≠ 0] ...(i)

=> \( \Large x \left(x^{2} - 12\right) = 0 \)

=> \( \Large x^{2} = 12 \)

Its total surface area

= \( \Large 6x^{2} = 6 \times \left(12\right) = 72 \  sq \  units \)