Mẫu: 75 + 25 + 46 = (75 + 25) + 46

                               = 100 + 46

                                = 146

37 + 8 + 3 = (37 + 3) + 8

                 = 40 + 8

                 = 48

a) 36 + 14 + 9

= (36 + 14) + 9

= 50 + 9

= 59

c) 65 + 9 + 5

= (65 + 5) + 9

= 70 + 9

= 79

b) 51 + 12 + 18

= 51 + (12 + 18)

= 51 + 30

= 81

d) 31 + 26 + 69

= (31 + 69) + 26

= 100 + 26

= 126