The volume of a cube is 68.921 ft.3 what is the length of each side?

Not enoggh deatil but
 \60.369      v       v      v       v     v  

A cube has equal sides so the volume is calculated as
V= a x a x a verses the Volume of a box which equals
lenght x height x width

Now we take the 3rd root of 68.921 by 3✔ ️because all sides are equal on a cube. We have 4.10 ft.

Check:
4.10 ft x 4.10 ft =
16.81 ft^2

16.81 ft^2 x 4.10 ft = 68.921 ft^3