SOLUTION: Determine the sets A, B where A − B {1, 3, 7, 11},I am not sure what is being asked with this question or where to begin to solve this.

A, B where A - B = {1, 3, 7, 11}

You haven't given all the information.  If you'll check your book
I think you will find something you left out.

Set subtraction:

A - B means to start with set A and take out any elements that A
has in it that are elements of B.  

For instance, let

A = {1,2,3,5,6,7,10,11,12}

and

B = {2,4,5,6,8,10,12,13}

then

A - B = {1,2,3,5,6,7,10,11,12} - {2,4,5,6,8,10,12,13} = {1,3,7,11}

Because we removed all the elements from A that were elements of B.
Note that we couldn't take 4, 8 and 13 out of A for A does not contain
them, so we just ignore them. 

Edwin