I can’t get this answer right

Find the greatest common factor of the followig monomials 21u^5v,3u^4v^6, and 3u^2v^5

Can you me find the missing length. i attached an image.

Awavelength of 610 nm was found to be the most intense wavelength emitted by copper. answer the following questions about this wavelength of light. a) what is this wavelength in cm? b) what is the frequency that corresponds to this wavelength? c) what is the energy of light of this wavelength? d) what is the wavenumber corresponding to this wavelength?