a)

160 : (4 × 8) = 160 : 32 = 5

160 : 4 : 8 = 40 : 8 = 5

Vậy 160 : (4 × 8) = 160 : 4 : 8.

96 : (3 × 8) = 96 : 24 = 4

96 : 3 : 8 = 32 : 8 = 4

Vậy 96 : (3 × 8) = 96 : 3 : 8.

105 : (5 × 7) = 105 : 35 = 3

105 : 5 : 7 = 21 : 7 = 3

Vậy 105 : (5 × 7) = 105 : 5 : 7.

Nhận xét: a : (b × c) = a : b : c

b)

270 : (9 × 6) = 270 : 9 : 6 = 30 : 6 = 5

420 : (7 × 3) = 420 : 7 : 3 = 60 : 3 = 20

144 : (2 × 8) = 144 : 2 : 8 = 72 : 8 = 9

X x 4 = 160                                                                        X : 5 = 151

X       = 160 : 4                                                                   X      = 151 x 5

X       = 40                                                                           X      = 755

`( 42 - x ) : 9 + 1 = 4`

`( 42 - x ) : 9 =4-1`

`( 42 - x ) : 9 =3`

`42-x=3xx9`

`42-x=27`

`x=42-27`

`x=15`

Vậy `=15`

`55 - 5 xx ( x + 1 ) = 20`

`5 xx ( x + 1 ) =55-20`

`5 xx ( x + 1 ) =35`

`x+1=35:5`

`x+1=7`

`x=7-1`

`x=6`

Vậy `x=6`

`164 - 64 : ( 12 + x ) = 160`

` 64 : ( 12 + x ) =164-160`

` 64 : ( 12 + x ) =4`

`12+x=64:4`

`12+x=16`

`x=16-12`

`x=2`

Vậy `x=2`

`@` `\text {Ans}`

`\downarrow`

`(42 - x) \div 9 + 1 = 4`

` (42 - x) \div 9 = 4 - 1`

` (42 - x) \div 9 = 3`

` 42 - x = 3 \times 9`

` 42 - x = 27`

` x = 42 - 27`

` x = 15`

______

`55 - 5 \times ( x + 1 ) = 20`

`5 \times (x+1) = 55 - 20`

`5 \times (x+1) = 35`

`x + 1 = 35 \div 5`

`x + 1 = 7`

`x = 7 - 1`

`x = 6`

______

`164 - 64 \div ( 12 + x ) = 160`

`64 \div (12 + x) = 164 - 160`

`64 \div (12 + x) = 4`

`12 + x = 64 \div 4`

`12 + x = 16`

`x = 16 - 12`

`x = 4`

`@` `\text {Kaizuu lv uuu}`

\(\left(42-x\right):9+1=4\)

\(\left(42-x\right):9=4-1\)

\(\left(42-x\right):9=3\)

\(42-x=3\times9\)

\(42-x=27\)

\(x=42-27\)

\(x=15\)

\(55-5\times\left(x+1\right)=20\)

\(5\times\left(x+1\right)=55-20\)

\(5\times\left(x+1\right)=35\)

\(x+1=35:5\)

\(x+1=7\)

\(x=7-1\)

\(x=6\)

\(164-64:\left(12+x\right)=160\)

\(64:\left(12+x\right)=164-160\)

\(64:\left(12+x\right)=4\)

\(12+x=64:4\)

\(12+x=16\)

\(x=16-12\)

\(x=4\)

x = 160 : 5

Bằng 32 vì lấy 160 chia 5 

\(160:x=5\left(đk:x\ne0\right)\)

\(\Leftrightarrow x=\dfrac{160}{5}\)

\(\Leftrightarrow x=32\left(tm\right)\)

( 160 x 5 - 25 x 4 ) : 4

<=> ( 800 - 100 ) : 4

<=> 700 : 4 

<=> 175 . đúng 100 % luôn 

nhớ ủng hộ nha

( 160 x 5 - 25 x 4 ) : 4

<=> ( 800 - 100 ) : 4

<=> 700 : 4

<=> 17

Chắc chắn 100%

  ( 160 x 5 - 25 x 4 ) : 4  . 

=( 800 - 100 ) : 4 . 

=700 : 4 . 

=175 . 

=>(x+x+...+x)+(5+7+9+...+15)=160                ( 6 số hạng x)

=>6*x+(15+5)*[(15-5):2+1]:2=160

=>6*x+20*6:2=160

=>6*x+60=160

=>6*x=160-60

=>6*x=100

=>x=100:6

=>x=50/3

\(\frac{y}{5}=\frac{x}{3};\frac{x}{7}=\frac{z}{8}\Rightarrow\frac{y}{35}=\frac{x}{21};\frac{x}{21}=\frac{z}{24}\Rightarrow\frac{x}{21}=\frac{y}{35}=\frac{z}{24}\)

Áp dụng tính chất dãy tỉ số bằng nhau, ta có :

\(\frac{x}{21}=\frac{y}{35}=\frac{z}{24}=\frac{x+y+z}{21+35+24}=\frac{160}{80}=2\)

\(\Rightarrow\frac{x}{21}=2\Rightarrow x=42\)

\(\Rightarrow\frac{y}{35}=2\Rightarrow y=70\)

\(\Rightarrow\frac{z}{24}=2\Rightarrow z=48\)

          #~Will~be~Pens~#

\(\hept{\begin{cases}\frac{x}{3}=\frac{y}{7}\\\frac{x}{7}=\frac{z}{8}\end{cases}\Leftrightarrow\hept{\begin{cases}\frac{x}{21}=\frac{y}{49}\\\frac{x}{21}=\frac{z}{24}\end{cases}\Leftrightarrow}}\frac{x}{21}=\frac{y}{49}=\frac{z}{24}\)

Áp dụng tính chất dãy tỉ số bằng nhau :

\(\frac{x}{21}=\frac{y}{49}=\frac{z}{24}=\frac{x+y+z}{21+49+24}=\frac{160}{94}=\frac{80}{47}\)

\(\Rightarrow\hept{\begin{cases}x=21.\frac{80}{47}=\frac{1680}{47}\\y=49.\frac{80}{47}=\frac{3920}{47}\\z=24.\frac{80}{47}=\frac{1920}{47}\end{cases}.}\)

#)Bạn #Đỗ Đức Lợi chép sai đề => làm bài cg sai lun rùi ( ai spam bài tui thế ??? làm đúng rùi mak @@ )

ta có:

\(\frac{x}{5}=y=\frac{z}{-2}\)=>\(\frac{-x}{-5}=\frac{-y}{-1}=\frac{2z}{-4}\)

Áp dụng tính chất của dãy tỉ số bằng nhau ta có:

\(\frac{-x}{-5}=\frac{-y}{-1}=\frac{2z}{-4}=\frac{-x-y+2z}{-5-1+\left(-4\right)}=\frac{160}{-10}=-16\)

=>\(\frac{x}{5}=-16\)=>x=-80

   \(y=-16\)

   \(\frac{z}{-2}=-16\)=>z=32

Vậy x=-80 ;y=-16 ;z=32