a. 13 × x > 12 × x (x khác 0)

b. 215 × 3 < 215 + 215 + 215 + 215

c. m × n > m – n (n khác 0, m lớn hơn hoặc bằng n)

\(215\times94+215\times5+215\)
\(=215\times\left(94+5+1\right)\)
\(=215\times100\)
\(=21500\)

215 × 94 + 215 × 5 + 215

= 215 × ( 94 + 5 + 1 )

= 215 × 100

= 21500

a, > 

b,>

c, <

a)>

b)>

c)<

1. Dien<;>;=

a) 13:x.     >.          12:x

b) 215:3.  >.           215-215+215-215

c) m:n.      <            m+n(n khac 0 va m lon hon hoac bang n)

= 215 x 85 + 215 x 1 + 215 x 14

= 215 x ( 85 + 14 +1 ) 

= 215 x 100

= 21500

Đáp án:

215 x 85 + 215 + 215 x 14

=215 x (85 + 14 +1)

=215 x 100

=21500

 215 x 85 +215 +215 x14

=215 x 85 +215 x 1 +215 x14

=215 x (85 + 1+14)

=215 x     100

=   21500

15*x-x=378

14*x=378

      x=378:14

      x=27

15*x-x=378

x*(15-1)=378

x*14 = 378

x= 378/14=27

15 * x - x = 378

(15-1)*x=378

14*x=378

x=378:14

x=27

15 * x - x      =378 

 15 * x - x * 1 = 378

 x * ( 15 - 1 )  = 378

 x * 14           = 37

 x                   = 378 : 14

x                      = 27

=>14*x=378

=>x=378:14

=>x=27

tk cho mik nhé

15 . x - x = 378

x . ( 15 - 1 ) = 378

x . 14 = 378

x = 378 : 14

x = 27

Vậy x = 27

xx - x . 2 = 378

x . 11 - x . 2 = 378

x . 9 = 378

x = 378 : 9 

x = 42

\(xx-x\times2=378\)

\(x\times11-x\times2=378\)

\(x\times9=378\)

\(x=42\)

\(=-\left(215+x\right)+215=-9\\ -\left(215+x\right)=-224\\ x=-9\)

\(-215-x+215=9\\ -215-x=9-215\\ -215-x=-206\\ x=-215-\left(-206\right)\\ x=-9\)

hoặc ta có thể tính  như sau :

\(=-\left(215+x\right)+215=-9\\ \Rightarrow x+\left[\left(-215\right)+215\right]=-9\\ \Rightarrow x+0=-9\\ \Rightarrow x=-9\)