Suppose C is a subset of D and D is a Subset of C.

Question

If n(c)=5,find n(D)
what other relationship exists between C and D

Answer 1

If C ⊂ D ∪ D ⊂ C
it implies C = D.
Thus if the cardinality of C is 5, the cardinality of D is also 5.
The other relationship is, as mentioned above, C = D.

Answer 2

Correction
If C ⊂ D ∩ D ⊂ C
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