Question 1208678
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In your post, you write


"I see pi, e, and another set containing elements x, y, and z ".



I do not see it.


What I see is pi, e, and the list {x,y,y} in curved brackets,
which contradicts to the rules of presenting sets, since the element "y" is repeated twice.



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Comment from student: Inside set B is another set. Let's call the other set a smaller box. 
It's like opening a box and finding a ball, glove and another box. We don't know what lies inside the smaller box. 
So, when I open the bigger box, I see three items: ball, glove and smaller box. 
So, the cardinality is 3. 
NOTE: I MADE A TYPO. THE SET INSIDE SET B SHOULD HAVE ELEMENTS X, Y, AND Z NOT X, Y, AND Y. 
WE DON'T REPEAT THE ELEMENTS IN A SET. YOU SAY?



<U>My response</U>: Correct.