вычислите с объяснением и проверкой

60-29, 27+54, 45+34, 76-18, 31-15, 23+49, 90-12, 56+32

60 - 29 = 60 - 30 + 1 = 30 + 1 = 31

27 + 54 = 30 - 3 + 60 - 6 = 90 - 9 = 81

45 + 34 = 45 + 35 - 1 = 80 - 1 = 79

76 - 18 = 76 - 20 + 2 = 56 + 2 = 58

31 - 15 = 30 + 1 - 15 = 15 + 1 = 16

23 + 49 = 23 + 50 - 1 = 73 - 1 = 72

90 - 12 = 90 - 10 - 2 = 80 - 2 = 78

56 + 32 = 56 + 30 + 2 = 86 + 2 = 88

Проверки.

29+31=60

81-27=54

79-34=45

58+18=76

16+15=31

72-23=49

78+12=90

88-32=56