Đáp án`+`Giải thích các bước giải:

Bài 3:

a) `250 : (10 - x) = 25`

`10 - x = 10`

`x = 0`

Vậy `x = 0`

b) `3x - 2018 : 2 = 23`

`3x - 1009 = 23`

`3x = 1032`

`x = 344`

Vậy `x = 344`

c) `(9x - 21) : 3 = 2`

`9x - 21 = 6`

`9x = 27`

`x = 3`

Vậy `x = 3`

d) `53 (9 - x) = 53`

`9 - x = 1`

`x = 8`

Vậy `x = 8`

e) `91 - 5 . (5 + x) = 61`

`5 . (5 + x) = 30`

`5 + x = 6`

`x = 1`

Vậy `x = 1`

f) `[195 - (3x - 27)] . 39 = 4212`

`195  - (3x - 27) = 108`

`3x - 27 = 87`

`3x = 114`

`x = 38`

Vậy `x = 38`

Bài 4:

Ta có:

`a = 2002 . 2002`

`a = 2000 . 2002 + 2 . 2002`

`a = 2000 . 2002 + 4004`

Ta có:

`b = 2000 . 2004`

`b = 2000 . 2002 + 2 . 2000`

`b = 2000 . 2002 + 4000`

Vì `4004 > 4000`

Nên `a > b`

Vậy `a > b`

꧁$\color{#1c1c1c}{\text{G}}$$\color{#2a2043}{\text{o}}$$\color{#291063}
{\text{d}}$$\color{#53008}{\text{M}}$$\color{#6b28ac}
{\text{a}}$$\color{#8c4ebd}{\text{t}}$$\color{#B592D6}
{\text{h}}$$\color{#ceaedf}{\text{s}}$꧂