a, 49 x 385 - 39 x 385

= 385 x ( 49 - 39)

= 385 x 10

= 3850

b, 46 x 17 + 38 x 46 + 46 x 44 + 46

= 46 x 17 + 38 x 46 + 46 x 44 + 46 x 1

= 46 x (17 + 38 + 44 + 1)

= 46 x 100

= 4600 

35 x 11 + 385 x 45 + 385 x 9 x 6 = 385 + 385 x 45 + 385 x 54 = 385 x (1 + 45 + 54) = 385 x 100 = 38 500

49 x 365 - 39 x 365

= (49-39) x 365

= 10 x 365 = 3650

a) 142 x 12 + 42 x 18

= 142 x (12 +18)

= 142 x 30 = 4260

b) 49 x 365 - 39 x 365

= (49-39) x 365

= 10 x 365 = 3650

c) 4 x 18 x 25

= 18 x (4 x 25)

= 10 x 100 = 1800

x - 4368 = 3484 x 4

x - 4368 = 13 936

x = 13 936 + 4368

x = 18 304

\(x\) - 4368 = 3484 x 4

\(x\) - 4368 = 13936

\(x\)          = 13936 + 4368

\(x\)         = 18304

\(x-4368=3484\times4\)

\(=>x-4368=13936\)

\(=>x=13936+4368\)

\(=>x=18304\)

 X - 4368 = 3484 x 4

x - 4368 = 13936

x = 13936 + 4368

x = 18304

 X - 4368 = 3484 x 4

 X - 4368 = 13936

  X = 13936 + 4368

  X = 18304

`x : 5/2 = 7/3`

`=> x= 7/3 xx 5/2`

`=>x= 35/6`

__

`23,7 xx 49 +23,7 xx 51`

`= 23,7 xx (49+51)`

`= 23,7 xx 100`

`=2370`

Lời giải:
a. 

$x=\frac{7}{3}\times \frac{5}{2}=\frac{35}{6}$

b.

$23,7\times 49+23,7\times 51=23,7\times (49+51)=23,7\times 100=2370$

x: 5/2=7/3`

`=> x = 7/3 xx 5/2`

`=> x=35/6`

Vậy `x = 35/6`

`23,7 xx 49 + 23,7 xx 51`

` =23,7 xx(49+51)`

`= 23,7 xx 100`

`=2370`

49 x 50 + 13 x 49 + 49

= 49 x ( 50 + 13 + 1 )

= 49 x 64

= 3136

Học tốt !!! ~

   49 x 50 + 13 x 49 + 49 

= 49 x 50 + 13 x 49 + 49 x 1 

= 49 x ( 50 + 13 + 1 )

= 49 x 64

= 3136

k mình nha

hihihiihihihihihihihihihihihihiihihihihihihiihihihihihihiihihihihih

a) 142 x 12 + 142 x 18

= 142 x ( 18 + 12 )

= 142 x 30

= 4260

b) 49 . 365 - 39 . 365

= 365 . ( 49 - 39)

= 365 . 10

= 3650

c) 4 . 18 . 25

= 18 . 4 . 25

= 18 . 100

= 1800

a, 142 x 12 + 142 x18=142 x (12+18)= 4260

b, 49 x 365 - 39 x356 = 356 x (49-39)= 3560

c,4 x 18 x 25 = (25 x 4) x 18=1800

a,142 x 12 + 142 x 18 

=142 x (12+18)

=4260

b,49 x 365 - 39 x 365

= 365 x ( 49 -39 )

=365 x 10

=3650

c,4 x 18 x 25

=(4 x 25 ) x 18

= 100 x 18

= 1800