Bài 1:
a) 38.67 – 38 - 38.14                                               b) 111-[63:62  +  4(9 - 4)2]
=  38.67 - 38.1 - 38.14                                          = 111- [ 61        +  4.  52]
= 38. (67-1-14)                                                     = 111- [ 6       +  4.  25]
= 38.  (66-14)                                                           = 111- [ 6       +   100  ]
=  38.     52                                                              =  111-          106
=               1976                                                    =          5

c) 75 + {5 . [81: (7- 4)2] + 15} : 10

=  75 + {5 . [81:    32      ] + 15} : 10

=  75 + {5 . [81:    9       ] + 15} : 10

=  75 + {5 .          9         + 15} : 10

=  75 + {45           + 15} : 10

=  75 +   60                     : 10

=  75 +        6

=        81

d) A= {-4; -3; -2; -1; 0; 1}

Số số hạng là:  [1- (-4)] :1 + 1 = 6 (số)

Tổng các số nguyên là: [1 + (-4)] x 6 : 2 = -9

Vậy tổng các số nguyên trong tập hợp A là -9

Bài 2:

a) 12x+16 = 2020                                            b) 20 + 5.(x – 4) = 120

    12x       = 2020 – 16                                              5.(x – 4) = 120 – 20

    12x       =       2004                                                   5.(x – 4) =    100

        x       =   2004  : 12                                                x – 4  = 100 : 5

        x       =        167                                                        x – 4  =    20

    Vậy x   = 167                                                               x        =  20 +4

                                                                                         x        =   24

                                                                           Vậy      x         =  24
c) 150 - 5.(x - 4) = 190                                    d) 92 - (3x – 125).11= 81

             5.(x - 4) = 150 – 190                                      (3x – 125).11 = 92 – 81

             5.(x - 4) = 150 + (-190)                                  (3x – 125).11 =       11

             5.(x - 4) =      -40                                             3x – 125        =  11 : 11

                 x – 4  = -40  : 5                                            3x – 125        =        1                        

                 x – 4  =  -8                                                   3x                   =  1 + 125                                              

                 x        = -8 + 4                                              3x                   =     126          

                 x        =   -4                                                    x                   =  126 : 3      

         Vậy x  =       -4                                                      x                   =      42                      

                                                                       Vậy      x                   =     42