find (i) A - B (ii) A - C (iii) A - D (iv) B - A (v) C - A (vi) D - A (vii) B - C (viii) B - D (ix) C - B (x) D - B (xi) C - D (xii) D - C

If A = {3, 6, 9, 12, 15, 18, 21}, B = {4, 8, 12, 16, 20}, C = {2, 4, 6, 8, 10, 12, 14, 16},
D = {5, 10, 15, 20};
find
(i) A - B
(ii) A - C
(iii) A - D
(iv) B - A
(v) C - A
(vi) D - A
(vii) B - C
(viii) B - D
(ix) C - B
(x) D - B
(xi) C - D
(xii) D - C
Answer
The difference of the sets A and B is the set of elements A which don’t belongs to set B
(i) A - B = {3, 6, 9, 15, 18, 21}
(ii) A - C = {3, 9, 15, 18, 21}
(iii) A - D = {3, 6, 9, 12, 18, 21}
(iv) B - A = {4, 8, 16, 20}
(v) C - A = {2, 4, 8, 10, 14, 16}
(vi) D - A = {5, 10, 20}
(vii) B - C = {20}
(viii) B - D = {4, 8, 12, 16}
(ix) C - B = {2, 6, 10, 14}
(x) D - B = {5, 10, 15}
(xi) C - D = {2, 4, 6, 8, 12, 14, 16}
(xii) D - C = {5, 15, 20}