A 10.0 m wire is hung from a high ceiling and held tightly below
by a large mass. Standing waves are created in the wire by air currents
that pass over the wire, setting it in motion. If the speed of the
standing wave is 335 m/s and its frequency is 67 Hz, what is its
wavelength?

5 m

Explanation:

Speed of waves is as the product of frequency and wavelength hence expressed as s=fw where f is the frequency of waves in Hz, s is the speed in m/s and w is wavelength in meters.

Making w the subject of the formula then

Substituting 335 m/s for s and 67 Hz for f then the wavelength is

Wavelength is the distance between successive crests. Since the string is 10m, wavelengths of 5m each will be 2 and the crests will be 3.

Wavelenth=5 m

one "light year" is the distance that light travels, through vacuum, in one julian year.   that's 365.25 days, of 24 hours each.