Tính bằng cách thuận tiện.

a) 92 + 74 + 26

b) 12 + 14 + 16 + 18

c) 592 + 99 + 208

d) 60 + 187 + 40 + 13

a) 92 + 74 + 26 = 92 + (74 + 26)

                          = 92 + 100 = 192

b) 12 + 14 + 16 + 18 = (12 + 18) + (14 + 16)

                                   = 30 + 30 = 60

c) 592 + 99 + 208 = (592 + 208) + 99

                                = 800 + 99 = 899

d) 60 + 187 + 40 + 13 = (60 + 40) + (187 + 13)

                                     = 100 + 200 = 300