A ∩ (B ∪ C)c Substitute the sets for the capital letters: {q, s, u, w, y} ∩ ({q, s, y, z} ∪ {v, w, x, y, z})c Do in the parentheses first which is a "∪", which means "union", so we combine the two sets on each side of the "∪" into one (we don't repeat the y or z, which are elements of both): {q, s, u, w, y} ∩ ({q, s, y, z, v, w, x})c Now we do the "c", which means "complement", by replacing it with all the elements of U, the universal set, that are not in {q, s, y, z, v, w, x} So when we remove all those from U, the universal set, we have this left {r, t, u} so that's the complement set. So now we have {q, s, u, w, y} ∩ {r, t, u} Now we do the "∩", which means "intersection", so we take only the elements that are common to both sets, and ignore all the others. So the final answer is {u}, which has only one element, and is called a "singleton". Answer: {u} Edwin