126,7 < 897

125,8<581,4

457>124

12:10 <254

b: =124-312+76-112+21

=200-424+21

=221-424

=-203

a: =735+23-135+177=600+200=800

b: =124-312+76-112+21=200-424+21=-203

c: =183+21+65-183-21=65

d: \(=-271+37-160+31-137=-500\)

e: =-3a+b-3c+b+3c+2a-2b

=-a

7x+24=-40-x

7x+x=-40-24

8x=-64

x=-64:8

x=-8

4x-10=-109+7x

4x-7x=-109+10

-3x=-99

x=-99:(-3)

x=-33

5x-77=-21-2x

5x+2x=77-21

7x=56

x=56:7

x=8

541-(2018-x)=-735

541-2018+x=-735

x=-735-541+2018

x=742

mình chỉ làm được vậy thôi.

chúc bạn học tốt

1) \(\frac{\sqrt{165^2-124^2}}{164}=\frac{\sqrt{\left(165-124\right)\left(165+124\right)}}{164}=\frac{\sqrt{41}\cdot\sqrt{289}}{164}=\frac{\sqrt{41}\cdot17}{164}=\frac{17}{4\sqrt{41}}\)

2) \(\frac{\sqrt{149^2-76^2}}{\sqrt{457^2-384^2}}=\frac{\sqrt{\left(149+76\right)\left(149-76\right)}}{\sqrt{\left(457+384\right)\left(457-384\right)}}=\frac{\sqrt{225}\cdot\sqrt{73}}{\sqrt{841}\cdot\sqrt{73}}=\frac{25}{29}\)

a: \(=\sqrt{\dfrac{25}{16}\cdot\dfrac{49}{9}\cdot\dfrac{1}{100}}=\dfrac{5}{4}\cdot\dfrac{7}{3}\cdot\dfrac{1}{10}=\dfrac{35}{120}=\dfrac{7}{24}\)

b: \(=\sqrt{1.44\cdot0.81}=1.2\cdot0.9=1.08\)

c: \(=\sqrt{\dfrac{\left(165-124\right)\left(165+124\right)}{164}}=\sqrt{\dfrac{1}{4}\cdot289}=\dfrac{17}{2}\)

d: \(=\sqrt{\dfrac{\left(149-76\right)\left(149+76\right)}{\left(457-384\right)\left(457+384\right)}}=\sqrt{\dfrac{225}{841}}=\dfrac{15}{29}\)

7 3 5   :   x   =   5 4 15   -   1 1 6 38 5   :   x   =   79 15   -   7 6 38 5   :   x   =   158 30   -   35 30 x   =   38 5   :   41 10   ⇒ x   =   76 41

Đáp án cần chọn là B

514+(218+x)=735 

218+x=735-514

218+x=221

x=221-218

x=3

vậy x=3

x=3