1.

$-7(5-x)-2(x-10)=15$

$-35+7x-2x+20=15$

$5x-15=15$

$5x=30$

$x=30:5=6$

2.

$3(x-4)-(8-x)=12$

$3x-12-8+x=12$

$4x-20=12$

$4x=12+20=32$

$x=32:4=8$

3.

$7(x-9)-5(6-x)=(-6)+11x$

$7x-63-30+5x=11x-6$

$12x-93=11x-6$

$12x-11x=93-6$

$x=87$

a.\(y:\dfrac{4}{5}=\dfrac{11}{8}\)

\(y=\dfrac{11}{8}\times\dfrac{4}{5}\)

\(y=\dfrac{11}{10}\)

b.\(\dfrac{11}{3}-y=\dfrac{1}{9}\)

\(y=\dfrac{11}{3}-\dfrac{1}{9}\)

\(y=\dfrac{32}{9}\)

c.\(\dfrac{1}{7}\times x=\dfrac{8}{5}\)

\(x=\dfrac{8}{5}:\dfrac{1}{7}\)

\(x=\dfrac{56}{5}\)

\(y=\dfrac{11}{8}.\dfrac{4}{5}\)

\(y=\dfrac{44}{40}\)

\(x=\dfrac{11}{3}-\dfrac{1}{9}\)

\(x=\dfrac{99-3}{27}=\dfrac{96}{27}\)

\(x=\dfrac{8}{5}:\dfrac{1}{7}\)

\(x=\dfrac{56}{5}\)

a)\(y=\dfrac{4}{5}\times\dfrac{11}{8}=\dfrac{44}{40}=1\dfrac{4}{40}\)

b)\(y=\dfrac{11}{3}-\dfrac{1}{9}=\dfrac{33}{9}-\dfrac{1}{9}=\dfrac{32}{9}\)

c)\(x=\dfrac{8}{5}\times7=\dfrac{56}{5}\)

a) ta có \(\frac{-5}{6}\)\(\times\)\(\frac{120}{25}\)< \(x\)<\(\frac{-7}{15}\)\(\times\)\(\frac{4}{9}\)\(\Rightarrow\)\(-4\)<\(x\)<\(-0,2074074074\)\(\Rightarrow\)\(-4\)<\(x\)<\(-0,2\)

mà \(x\)\(\in\)\(ℤ\)\(\Rightarrow\)\(x\)\(\in\)( -1;-2;-3)

b) ta có \(\left(\frac{-5}{3}\right)^3\)<\(x\)<\(\frac{-25}{35}\)\(\times\)\(\frac{-5}{6}\)\(\Rightarrow\)\(-4,62962963\)<\(x\)<\(0,5952380952\)

mà \(x\)\(\in\)\(ℤ\)\(\Rightarrow\)\(x\)\(\in\)(-4;-3;-2;-1;0)

ĐÚNG THÌ K CHO MK NHA

Mơn bạn nha 

forever young

>_<

!!!!!!!!!!

cậu muốn gì hả Kurama

25.35.4

=25.4.35

=100.35

=3500

5.15.2

=5.2.15

=10.15

=150

x-9=0

    x=0+9

    x=9

x+10=10

      x=10-10

      x=0

25. 35 . 4 = ( 25 . 4 )  .35 = 100 . 35 = 3500

5 . 15 . 2 = ( 5 . 2 ) . 15 = 10 . 15= 150

Bài 2 : 

x - 9 = 0 => x = 0 + 9  => x = 9. Vậy x = 9

x + 10 = 10 => x = 10 - 10 => x = 0. Vậy x = 0

a) 1+2+3+...+2018

=[(2018-1):1+1].(2018+1):2

=2018.2019:2

=2037171

b) 4+7+10+13+...+2017

=[(2017-4):3+1].(2017+4):2

=672.2021:2

=679056

c) 1+2-3-4+5+6-7-8+9+10-11-12+13+14

=(1+2-3-4)+(5+6-7-8)+(9+10-11-12)+13+14

=-4+(-4)+(-4)+13+14

=-12+27

=15

d) 23 x 75 + 25 x 23 + 180

=23 x (75+25) +180

=23 x 100 +180

=2300+180

2480

chúc ban hoc tốt nha

a) Số số hạng: ( 2018 - 1 ) : 1 + 1 = 2018

   Tổng:           2018 x ( 2018 + 1 ) : 2 = 2 037 171

b) Số số hạng: ( 2017 - 4 ) : 3 + 1 = 672

    Tổng: 672 x ( 2017 + 4 ) : 2 = 679 056

\(\text{1, (32-x)+(-7+/x/)-(/-x/+25)-45}=32-x-7-x-x-25-45\)

\(=-45-3x\)

Tui tính nv đó.

Học tốt

#Thảo Vy#

c, 200 - ( 2x + 6 ) = 4 ^ 3

   200 - ( 2x + 6 ) = 64

             2x + 6   = 200 - 64

             2x + 6   = 136

             2x    =   136 - 6

             2x = 130

             x = 130 : 2 

             x = 65

a, 25 + 3 ( x - 8 ) = 106 

3( x - 8 ) = 106 - 25

3( x - 8 ) = 81

   x - 8 = 81 : 3

   x - 8 = 27

x = 27 + 8 

x = 35 .

`4/7 xx x -2/3=1/5`

`=> 4/7 xx x = 1/5+2/3`

`=> 4/7 xx x = 3/15 +10/15`

`=> 4/7 xx x =13/15`

`=> x= 13/15 : 4/7`

`=> x=13/15 xx 7/4`

`=> x= 91/60`

`4/7xx` `x-2/3=1/5`

`7/7xx` `x=3/15+10/15`

`4/7xx` `x=13/15`

`x=13/15:4/7`

`x=13/15xx4/7`

`x=91/60`

Vậy `x=91/60`

`@Nae`

1)

3*(x+1)-12=15                        4*(x-3)+12=40

=> 3*(x+1)=27                       => 4*(x-3)=28

=> x+1=9                              => x-3=7

=> x=8                                  => x=10

tui nhầm ở câu cuối đó 6 * 19 * 4 + 3 * 81* 8

mình nhầm câu cuối 6*19*4+3*81*8