Question 165529
Suppose C is a subset of D and D is a subset of C.
a. If n(C)= 5, find n(D).
b. What other relationship exists between sets C and D?
<pre><font size = 4 color = "indigo"><b>
Notice this does not say "PROPER subset", but just "subset".
 
The only way two sets can be subsets of each other is for
them both to be the same set.  So there really aren't two
sets, but just one.

So C and D are the same set, or C=D.

That's the answer to (b), then obviously n(D) = n(C) = 5 
is the answer to (a).

Edwin</pre>