(i) A - B is the set of all elements of A that are not in B. Both sets share 4 and 8, so we remove these from A to get
A - B = {1, 7}
(ii) Similarly,
B - A = {6, 9}
because both A and B contain 4 and 8.
(iii) We've actually already done this to get the relative complements in (i) and (ii). Both sets contain 4 and 8, so their intersection is
A ∩ B = {4, 8}