SOLUTION: Let U = {q, r, s, t, u, v, w, x, y, z} A = {q, s, u, w, y} B = {q, s, y, z} C = {v, w, x, y, z}. Determine the following. A ∪ (B ∩ C)

"∪" = UNIOM
∪ means to form the set consisting of every element that is either a member
of the set on the left of ∪ or a member of the set on the right of ∪.

"∩" = INTERSECTION
∩ means to form the set consisting of ONLY those elements that are in common
to both the set on the left of ∩ and to the set on the right of ∩. 

 Substitute the sets for the letters: 

                      A        ∪ (      B       ∩        C        )
               {q, s, u, w, y} ∪ ( {q, s, y, z} ∩ {v, w, x, y, z} )

First we work inside the parentheses, it has ∩, so we form the
set consisting of ONLY those elements that are incommon to both sets
{q, s, y, z} and {v, w, x, y, z}.  We see that y and z are the only
ones that are in common to both sets, so the set to form is {y, z}.
So far we have:

                      A        ∪ (      B       ∩        C        )
               {q, s, u, w, y} ∪ ( {q, s, y, z} ∩ {v, w, x, y, z} )
               {q, s, u, w, y} ∪              {y, z}              

Now we have only a ∪, and so we form the set that consists of all the
elements in {q, s, u, w, y} together withe both elements of {y, z}. So
we end up with this:
                      A        ∪ (      B       ∩        C        )
               {q, s, u, w, y} ∪ ( {q, s, y, z} ∩ {v, w, x, y, z} )
               {q, s, u, w, y} ∪              {y, z}
                                {q, s, u, w, y, z}

[Notice that we only need to list the y one time even though it is a
member of both sets.]

Edwin