No, it's always okay to ask if you don't understand a question. Anyway, for this problem, we just have to plug in the value for V to solve for P :
[tex]P = 4V^{ \frac{1}{3}} \\ P = 4(125)^{ \frac{1}{3}}[/tex]
A number to the power of 1/3 is the same as taking a cube root.
[tex]P = 4(125)^{ \frac{1}{3}} \\ P = 4(5) \\ P=20[/tex]
The perimeter of one face of the cube is 20m.
