P = {2, 3, 5, ..., 13}
Q = {7, 6, 5, ..., 1}
R = {2, 4, 6, ..., 14}
P - (Q ∪ R) = … .
{11, 13}
{1, 4, 6, 8, 10, 12}
{1, 4, 6, 8, 10, 12, 14}
{1, 4, 6, 8, 10, 11, 14}