Hi, I'm wondering how I would decide how many "subspaces of each dimension [tex]Z_2^3 [/tex] has." The answer is: 1 subspace with dim = 0, 7 with dim = 1, 7 with dim = 2, 1 with dim = 3. I'm looking for subsets of [tex]Z_2^3 [/tex] which are closed under addition and scalar multiplication. An arbitrary vector in [tex]Z_2^3 [/tex] is (a,b,c) where [tex]a,b,c \in Z_2 [/tex]. I can't think of a general way to do this, trial and error is a possibility and quite time consuming. So I think that there is some concept being tested which I'm not seeing. Any set consisting of a single vector with the zero vector in Z_2 would be a subspace since it would be closed under addition. But what about sets with 3 or more elements. I'm not sure how to approach this question. Can someone please help me out?