suppose I have 3 vectors, a b and c that form an orthonormal basis. How would I find a vector v = (1,2,3) in the a b c system? I don't really understand what its asking. Do I have to find a linear combination from a b c that forms v?

so basically for some scalars x y and z, I have to find

xa + by + cz = v?

if I'm right, how would I go about doing that?