Please answer in the form of a number

Answer:
d ≈ 8.3
Step-by-step explanation:
This is kind of like the pythagorean theorem, but with one extra value. Thus, [tex]d^2=l^2+w^2+h^2[/tex].
Plug in the values to get:
[tex]d^2=2^2+7^2+4^2\\d^2=4+49+16\\d^2=69\\d=\sqrt{69} \\[/tex]
Thus d ≈ 8.3