MHB Having difficulty finding the elements in each set

[chelseajjc95]

Find the elements in each set given that:

U={1,2,3,4,5,6,7}
A={1,3,5,7}
B={2,4,6}
C={1,2,5,6}
D={2,3,4}

A) C intersect D B) C-D C) (A union B) union C D) (C union A)' -D

 

[MountEvariste]

Where do the difficulties lie? Do you know what X intersect Y means, for example?

 

[HOI]

[math]X\cap Y[/math], "X intersect Y", means "all things that are in both set X and set Y". Here you are given that C= {1, 2, 5, 6} and D= {2, 3, 4}. "1" is in C but not in D so is NOT in [math]C\cap D[/math]. "2" is in both C and D so is in [math]C\cap D[/math]. "5" is in C but not in D so in NOT in [math]C\cap D[/math]. "6" is in C but not in D so NOT in [math]C\cap D[/math]. We don't need to consider either "3" or "4" since they are not in C. [math]C\cap D= \{1, 2, 5, 6\}\cap \{2, 3, 4\}= \{2\}[/math].

"X- Y" is defined as "all things that are in X but NOT in Y". "1", "5", and "6" are in C but not in D so [math]C- D= \{1, 5, 6\}[/math].

Now try the others. How are "X union Y" and "X' " defined?