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| Question 320024:  Given these sets:
 A = {1, 2, 3, 4}
 B = {3, 4, 5, 6, 7}
 C = {3, 5, 7, 9}
 
 List the elements of this set
 A ∩ (B U C)
 
 Note: The "U" in between the B and C is not really a U, but suppose to be a symbol like an uppercase U.
 Answer by Edwin McCravy(20064)
      (Show Source): 
You can put this solution on YOUR website! 
Given these sets:
A = {1, 2, 3, 4}
B = {3, 4, 5, 6, 7}
C = {3, 5, 7, 9}
List the elements of this set
A ∩ (B U C) 
Substitute the sets for the letters:
    A     ∩ [     B      U     C    ]
    |             |            |  
{1,2,3,4} ∩ [{3,4,5,6,7} U {3,5,7,9}]
We do the part in [ ] first.  To take the union of {3,4,5,6,7} and {3,5,7,9}
and make a set with elements that are in one or the other or both. So
we replace the bracketed expression by {3,4,5,6,7,9}
    A     ∩ [     B      U     C    ]
    |             |            |  
{1,2,3,4} ∩ [{3,4,5,6,7} U {3,5,7,9}]
{1,2,3,4} ∩ [     {3,4,5,6,7,9}]
and that is just
      {1,2,3,4} ∩ {3,4,5,6,7,9}
To take the intersection we may use ONLY elements which are in common
to both sets.  So the final answer is
              {3,4}
because 3 and 4 are the only elements in common to both sets.
Edwin
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