The volume of cuboid is V = 252 ft^3.
The width of cuboid is w = 14 ft.
The height of cuboid is h = 6 ft.
The formula for the volume of cuboid is,
[tex]V=l\cdot w\cdot h[/tex]Substitute the values in the formula to determine the length of cuboid.
[tex]\begin{gathered} 252=l\cdot14\cdot6 \\ l=\frac{252}{84} \\ =3 \end{gathered}[/tex]So length (missing dimension) of the cuboid is 3 ft.