Question

How much ribbon with a bow do I need to wrap a box that is 7" x 5" x 3"?

Answer 1

(2*7) + (2*5) + (2*3) = _______ inches

Add a generous amount for the bow.

Answer 2

Actually, I think you need to wrap two loops around the box, at right angles to each other: one the long way, one the short way. So, I'd use
2(7+3) + 2(5+3)
Or even more, depending on which two pairs of faces you wrap the ribbon on.