pls help me I don't understand

Answer:
[tex]d. \: \: \: 25 {x}^{6} [/tex]
Step-by-step explanation:
Given,
Side of the square
[tex] = 5 {x}^{3} [/tex]
Therefore, area of the square = side × side
[tex] = {5x}^{3} \times 5 {x}^{3} [/tex]
[tex] = 5 \times 5 \times {x}^{3 + 3} [/tex]
[tex] = 25 {x}^{6} [/tex]