28 - (96-74) = 100 - (36+11) = 19 + (61-) = 83 + (96-79) = 61 - (33+18) = 46 + (93-68) = y-55=34 13+x=91

В первую очередь действия выполним в скобках.

28 - (96 - 74) = 28 - 22 = 6;

100 - (36 + 11) = 100 - 47 = 53;

19 + (61-) = 19 + 61 = 80;

83 + (96 - 79) = 83 + 20 = 103;

61 - (33 + 18) = 61 - 51 = 10;

46 + (93 - 68) = 46 + 25 = 71;

y - 55 = 34;

у = 34 + 55;

у = 89;

89 - 55 = 34;

34 = 34.

13 + x = 91;

х = 91 - 13;

х = 78;

13 + 78 = 91;

91 = 91.