Determine the sets A, B where
A - B = {1, 3, 7, 11}
From that we have:
1 ∈ A, 1 ∉ B
3 ∈ A, 3 ∉ B
7 ∈ A, 7 ∉ B
11 ∈ A, 11 ∉ B
B - A= {2, 6, 8},
From that we have:
2 ∈ B, 2 ∉ A
6 ∈ B, 6 ∉ A
8 ∈ B, 8 ∉ A
A ∩ B = {4, 9}
From that we have:
4 ∈ A, 4 ∈ B, 9 ∈ A, 9 ∈ B
So we end up with
A = {1,3,7,11,4,9}, B = {2,6,8,4,9}
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C - D = {1, 2, 4},
From that we have:
1 ∈ C, 1 ∉ D
2 ∈ C, 2 ∉ D
4 ∈ C, 4 ∉ D
D − C = {7, 8},
From that we have:
7 ∈ D, 7 ∉ C
8 ∈ D, 8 ∉ C
C ∪ D = {1, 2, 4, 5, 7, 8, 9}
Since 5 and 9 are not in either C - D or in D - C,
they must be elements of both sets, since they were
removed in both cases of set subtraction. Therefore
C = {1,2,4,5,9}, D = {7,8,5,9}
Edwin