a. = 53 x (39 - 21) + 47 x (39 - 21)

= 53 x 18 + 47 x 18

= (53 + 47) x 18

= 100 x 18

= 1800

b. = 24 x 53 + 24 x 87 - 24 x 40

= 24 x (53 + 87 - 40)

= 24 x 100

= 2400

a)341(67+16)+659 X 83

=83(341+659)

=83000

trời ơi! Không giống như câu hỏi mà tôi tìm kiếm

a 1800

b 2400

a) 53.39 + 47.39 - 53.21 - 47.21
= 53.(39 - 21) + 47.(39 - 21)
= 53.18 + 47.18
= 18.(53 + 47)
= 18.100
= 1800

b) = ( 2 x 12 ) x 53 + ( 4 x 6 ) x 87 - ( 3 x 8 ) x 40

   =  24 x 53 + 24 x 87 - 24 x 40

   = 24 x ( 53 + 87 - 40 )

   = 24 x 100 

   = 2400

Chúc bạn học tốt :3

a, (9.x-21) : 3 = 2

=>9x-21=6

=>9x=27

=>x=3

b, (x-39)-21=0

=>x-39-21=0

=>x-60=0

=>x=60

c, 231+(312-x)=531

=>231+312-x=531

=>543-x=531

=>x=543-531

=>x=12

d, 53.(9-x)=53

=>9-x=1

=>x=8

a/ \(\frac{\left(9x-21\right)}{3}=2\)

\(\Rightarrow9x-21=2\cdot3=6\)

\(\Rightarrow9x=6+21=27\)

\(\Rightarrow x=\frac{27}{9}=3\)

b/ \(\left(x-39\right)-21=0\)

\(\Rightarrow x-39=0+21=21\)

\(\Rightarrow x=21+39=60\)

c/ \(231+\left(312-x\right)=531\)

\(\Rightarrow312-x=531-231=300\)

\(\Rightarrow x=312-300=12\)

d/ \(53\cdot\left(9-x\right)=53\)

\(\Rightarrow9-x=\frac{53}{53}=1\)

\(\Rightarrow x=9-1=8\)

( 1/2 + 1/3 ) x 2/5

c1 = 5/6 x 2/5 = 1/3

c2 = 1/2 x 2/5 + 1/3 x 2/5

= 1/5 + 2/15 

= 1/3

3/5 x 17/21 x 2/5

c1 := 17/35 x 2/5 = 34/175

c2 : = (3/5 x 2/5) x 17/21 

= 6/25 x 17/21 

= 34/175?

( 1/3 - 1/5 ) x 1/2

c1 : = 2/15 x 1/2 

= 1/15

c2 : = 1/3 x 1/2 - 1/5 x 1/2

= 1/6 - 1/10

= 1/15

c.53 ×39+47×39 + 53 x 21 + 47 x 21=6000

D . 2 x 53 x 12 + 4 x 6 x 87 - 3 x 8 x 40=2400

học tốt

C ) = 39 . ( 53 + 47 ) + 21 . ( 53 + 47 )

      = 39 . 100 + 21 . 100

      = (39 + 21) . 100

      = 60 . 100

      = 6000

D ) = 24 . 53 + 24 . 87 - 24 . 40

      = 24 . ( 53 + 87 - 40 )

      = 24 . 100

      = 2400

a, 53 x 39 + 47 x 39 - 53 x 21 - 47 x 21

= 53 x (39-21) + 47 x (93-21)

=53 x 18 + 47 x 18

= (53 +47) x 18

=100 x 18

=1800

b,2 x 53 x 12 + 4 x 6 x 87 - 3 x 8 x 40

=24 x 53 + 24 x 87 - 24 x 40

=24 x (53+87-40)

=24 x 100

=2400

c,5 x 7 x 77 - 7 x 60 +49 x 25 -15 x 42.

=5 x 7 x 77 - 7 x 5 x 12 +49 x 5 x 5 - 5 x 3 x 42.

=5 x 539 - 84 x 5 +245 x 5 -5 x 126

=5 x (539 - 84 +245 -126)

=5 x 574

=2870

tính nhanh cơ

a) =(53+47)*34-(53-47)*21=100x34-6x21=3400-126=3274

b)=(100-2)*2+1-(97+1)/2-1=197-50=147

chon cho minh nhe ban

39. ( 47+ 53 )-21

= 3900-21

= 3811

tính nhanh 210+47*4+16*47

=-175 bạn ạ

-175 nhé