даны множества p={8;10;12;17;21}, q={17;21;25;28;30}, r={10;12;17}
найти: (PUQ)\(PUR)

P U Q = {8, 10, 12, 17, 21, 25, 28, 30}P U R = {8, 10, 12, 17, 21}(P U Q) \ (P U R) = {25, 28, 30}