y = 57

y = 91/9

Y × 4 + 6 × Y = 570

Y × ( 4 + 6 ) = 570

Y × 10 = 570 

Y          = 570 : 10

Y          = 57 

Y × 5 +  4 × Y = 918 

Y × ( 5 + 4 ) = 918 

Y  ×   9 = 918

Y           = 918 : 9 

Y           =  102 

A, m x 3 + m x 7 = 1530
    m x (3+7)       = 1530
    m x 10            = 1530
⇒ m = 153
 B, m x 13 - 4 x m = 918
     m x (13-4)       = 918
     m x 9               = 918
⇒ m = 102
 

a) m x (3+7)=1530

m x 10=1530

m=1530/10

m=153

b)m x (13-4)=918

m x 9=918

m=918/9

m=102

Bạn coi lại đề. Dấu bị lỗi.

đề đúng mà cậu , dấu bị lỗi là sao ? mình ghĩ rõ ben dưới dấu chấm là x còn gì '-'

Bài 15:

a: 2x+x=45

=>3x=45

=>\(x=\frac{45}{3}=15\)

b: 2x+7x=918

=>\(x\cdot\left(7+2\right)=918\)

=>9x=918

=>\(x=\frac{918}{9}=102\)

c: 2x+3x=60+5

=>5x=65

=>\(x=\frac{65}{5}=13\)

d: \(11x+22x=33\cdot2\)

=>33x=66

=>\(x=\frac{66}{33}=2\)

Bài 14:

a: (12-x)(2-x)=0

=>\(\left[\begin{array}{l}12-x=0\\ 2-x=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=12\\ x=2\end{array}\right.\)

b: (x-33)(11-x)=0

=>\(\left[\begin{array}{l}x-33=0\\ 11-x=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=33\\ x=11\end{array}\right.\)

c: (21-x)(12-x)=0

=>\(\left[\begin{array}{l}21-x=0\\ 12-x=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=21\\ x=12\end{array}\right.\)

d: (50-x)(x-150)=0

=>\(\left[\begin{array}{l}50-x=0\\ x-150=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=50\\ x=150\end{array}\right.\)

Bài 13:

a: (x-2)(x-3)=0

=>\(\left[\begin{array}{l}x-2=0\\ x-3=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=2\\ x=3\end{array}\right.\)

b: (x-3)(x-4)=0

=>\(\left[\begin{array}{l}x-3=0\\ x-4=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=3\\ x=4\end{array}\right.\)

c: (x-7)(6-x)=0

=>\(\left[\begin{array}{l}x-7=0\\ 6-x=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=7\\ x=6\end{array}\right.\)

d: (x-3)(x-13)=0

=>\(\left[\begin{array}{l}x-3=0\\ x-13=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=3\\ x=13\end{array}\right.\)

m = 918 : ( 13 - 4 )

= 918 : 9= 102

m = 102 

a)  x x 4 + 6 x x  = 570

     x x (4 + 6)     = 570

     x x 10            = 570

     x                    = 570 : 10

     x                    = 57

 b) x x 5 + 4 x x  = 918

     x x (5 + 4)      = 918

     x x 9              = 918

     x                    = 918 : 9

     x                    = 102

a. X x 4 + 6 x X = 570

   X x ( 4+6) = 570

   X x 10 = 570

   X = 57

b. x x ( 5+4)= 918

    x x 9 = 918

    x = 918 : 9

    x = 102