theory of computations

3. The relation x y if and only if x y mod 3 is an equivalence relation. Use this equivalence relation to partition the set {1,7,12,14,15,16,19, 33, 34, 35) into equivalence classes. 4. How many substrings "bba" are there in wwRvw, where w aabbab? 5. Explain why there is no language L, such that (L*)'- (L)*. Note: the apostrophe means complement