The surface area of a cube is computed as:
6*A,
where A is the area of each of the 6 sides.
So we know that each of the sides has an area of
600/6 = 100 cm^2
The area of the sides of the cube is
A_side = s^2
where s is the side length.
So the side length is the square root of 100 cm^2
s = sqrt(100cm^2) = 10cm.
This means the side length is 10 cm.