=> 45-30-x=x-27+48

=> 15-x= x+21

=> 15-x+x=x+21+x

=> 15= 2x+21

=> 2x=15-21

=> 2x=(-6)

=> x=(-6):2

=> x= (-3)

25 x 27 + 45 x 27 + 27 x 30

= 27 x ( 25 + 45 + 30 )

= 27 x ( 70 + 30 )

= 27 x 100

= 2700

k cho mk nha !

= 27 x ( 25 + 45 + 30 )
= 27 x 100
= 2700

2700 nha bn

a) x = 25 ;26 

b) x = 0;1;2;3;4;...........;28;2930

c) x= 82; 83;84;85;86;87;88;89;90;91;92;93

d) x = 92

x = 25 ; 26

x = 0 ; 1 ; 2 ; ... ; 30

x = 82 ; ... ; 92

x = 92

24 < x < 27

=> x = 24, 25 , 26

a,

=85.35-85.27-35.85+35.27

=85.35+85.(-27)-35.85+35.27

=85[35+(-27)+(-35)]+35.27

=85.(-27)+35.27

=-85.27+35.27

=27.[(-85)+35]

=27.(-50)

=-1350

các câu còn lại cũng vậy

a, 85 x ( 35- 27 ) - 35 x ( 35 - 27 )

85 x 8 - 35 x 8

8 x ( 85 - 35 ) 

8 x 50 = 400

b, ( -45 ) x 69 + 30 x ( -45 ) +( -45)

( -45 ) x ( 69 + 30 + 1)

-45 x 100 = -4500

c , 26 + 7 x ( 4 - 12 )

26 + 7 x ( - 8 )

26 + ( -56 )=(- 30)

d , 127 - 18 x ( 5 + 6 )

127 - 18 x 11

127 - 180 + 18

-53 + 18 = - 35

a.85x(35-27)-35x(85-27)

=85x8-35x58

=680-2030

=(-1350)

b.(-45)x69+30x(-45)+(-45)

=(-3105)+(-1350)+(-45)

=1800+(-45)

=1755

c.26+7x(4-12)

=26+7x(-8)

=26+(-56)

=(-30)

d.127-18x(5+6)

=127-18x11

=127-198

=(-71)

li-ke cho mình nha bạn

a, x = 28

b, x = 1

c, x = 24

d, x = 3

(-45)=70-x

x = 70 - ( -45 )

x = 115

48-60=x-(-88)

-12 = x +88

x = -12 - 88

x = -100

45-(30-60)=9-x

45 - ( -30 ) = 9 - x

75 = 9 - x

x = 9 - 75 

x = -66

(-45)=70-x

x = 70 - (-45)

x = 115

vậy____

48-60=x-(-88)

-12 = x-(-88)

x = (-88)+12

x = -76

vậy____

45-(30-60)=9-x

45 - (-30) = 9-x

75 = 9-x

x = 9-75

x = -66

vậy____

(-45)=70-x

\(\Rightarrow\) 70 - x = -45

                x = 70 - ( -45 ) 

                x = 115

Vậy x = 115 .

48-60=x-(-88)

\(\Rightarrow\) x - ( -88 ) = 48 - 60

         x - ( -88 ) = -12

         x             = ( -12 ) + ( -88 )

         x             = -100

Vậy x = -100 .

45-(30-60)=9-x

\(\Rightarrow\) 9 - x = 45-(30-60)

         9 - x = 75

              x = 9 - 75

              x = 66

Vậy x = 66

:D

Đề sai:

\(\dfrac{45-x}{1968}+\dfrac{40-x}{1973}+\dfrac{35-x}{1978}+\dfrac{30-x}{1983}=-4\)

\(\Rightarrow\left(\dfrac{45-x}{1968}+1\right)+\left(\dfrac{40-x}{1973}+1\right)+\left(\dfrac{35-x}{1978}+1\right)+\left(\dfrac{30-x}{1983}+1\right)=0\)

\(\Rightarrow\dfrac{2013-x}{1968}+\dfrac{2013-x}{1973}+\dfrac{2013-x}{1978}+\dfrac{2013-x}{1983}=0\)

\(\Rightarrow\left(2013-x\right)\left(\dfrac{1}{1968}+\dfrac{1}{1973}+\dfrac{1}{1978}+\dfrac{1}{1983}\right)=0\)

Vì \(\dfrac{1}{1968}+\dfrac{1}{1973}+\dfrac{1}{1978}+\dfrac{1}{1983}\ne0\) nên \(2013-x=0\Leftrightarrow x=2013\)

a)Ta có: \(2x=3y;5y=7z\)và \(x-y-z=-27\)

\(\Rightarrow\frac{x}{3}=\frac{y}{2};\frac{y}{7}=\frac{z}{5}\)và\(x-y-z=-27\)

\(\Rightarrow\frac{x}{21}=\frac{y}{14}=\frac{z}{10}\)và \(x-y-z=-27\)

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

\(\frac{x}{21}=\frac{y}{14}=\frac{z}{10}=\frac{x-y-z}{21-14-10}=\frac{-27}{-3}=9\)

Ta có:\(\frac{x}{21}=9\Rightarrow x=9.21=189\)

          \(\frac{y}{14}=9\Rightarrow y=9.14=126\)

         \(\frac{z}{10}=9\Rightarrow z=9.10=90\)

Vậy:\(x=189;y=126\)và\(z=90\)

b) \(\frac{x}{4}=\frac{y}{5}=\frac{z}{6}\)và\(x^2-2y^2+z^2=18\)

\(\Rightarrow\frac{x^2}{16}=\frac{2y^2}{50}=\frac{z^2}{36}\)và\(x^2-2y^2+z^2=18\)

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

\(\frac{x^2}{16}=\frac{2y^2}{50}=\frac{z^2}{36}=\frac{x^2-2y^2+z^2}{16-50+36}=\frac{18}{2}=9\)

Ta có:\(\frac{x^2}{16}=9\Rightarrow x^2=144\Rightarrow\orbr{\begin{cases}x=12\\x=-12\end{cases}}\)

\(\frac{2y^2}{50}=9\Rightarrow2y^2=450\Rightarrow y^2=225\Rightarrow\orbr{\begin{cases}y=15\\y=-15\end{cases}}\)

\(\frac{z^2}{36}=9\Rightarrow z^2=324\Rightarrow\orbr{\begin{cases}z=18\\z=-18\end{cases}}\)

Vậy: \(x=12;y=15;z=18\)hoặc \(x=-12;y=-15;z=-18\)

c) \(x:y:z=3:8:5\)và\(3x+y-2z=14\)

\(\Rightarrow\frac{x}{3}=\frac{y}{8}=\frac{z}{5}\)và\(3x+y-2z=14\)

\(\Rightarrow\frac{3x}{9}=\frac{y}{8}=\frac{2z}{10}\)và \(3x+y-2z=14\)

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

\(\frac{3x}{9}=\frac{y}{8}=\frac{2z}{10}=\frac{3x+y-2z}{9+8-10}=\frac{14}{7}=2\)

Ta có: \(\frac{3x}{9}=2\Rightarrow3x=18\Rightarrow x=6\)

\(\frac{y}{8}=2\Rightarrow y=16\)

\(\frac{2z}{10}=2\Rightarrow2z=20\Rightarrow z=10\)

Vậy:\(x=6;y=16;z=10\)

Bài 3: 

a: =>x=13-24=-11

b: =>3x=12

hay x=4