can somebody solve this question

)3. a) Define vector space and determine whether the set of all positive real numbers u with the operations u @ v = uv and cou = u' is a vector space? b) Express v = (3,7, -4) as a linear combination of x = (1,2,3), y = (2,3,7), 2 = (3,5,6) , also check whether the vectors x, y, z are linearly dependent or independent