Ta có: A = 12 : {390 : [500 - 370)]}

= 12 : {390 : 130}

=12 : 3

=4 

Ta có: A = 12 : {390 : [500 - 370)]}

= 12 : {390 : 130}

=12 : 3

=4 

A=12:{390:[500-(125+35x7)]}

=12:{390:[500-(125+245)]}

=12:{390:[500-370]

=12:{390:130}

=12:3

=4

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LƯU Ý: Thực hiện theo thứ tự ( trước , sau đó đến [ sau đó đến {

a. \(678\times\left(276+49\right)-678\times\left(149+76\right)\)

\(=678\times\left[\left(276+49\right)-\left(149+76\right)\right]\)

\(=678\times\left(276+49-149-76\right)\)

\(=678\times\left(200-100\right)\)

\(=67800\)

b. \(23\times157+15\times46-28\times87\)

\(=3611+690-2436\)

\(=1865\)

c. \(12:\left\{390:\left[500-\left(125+35\times7\right)\right]\right\}\)

\(=12:\left\{390:\left[500-\left(125+245\right)\right]\right\}\)

\(=12:\left\{390:\left[500-370\right]\right\}\)

\(=12:\left\{390:130\right\}\)

\(=12:3\)

\(=4\)

12:{390:[500-125+35x7]}

=12:{390:620}

=12:39/62

=248/13

cám ơn nhé !

\(12:\left\{390:\left[500-\left(125+35\cdot7\right)\right]\right\}\)

\(=12:\left\{390:\left[500+370\right]\right\}\)

\(=12:\left\{390:870\right\}\)

\(=12:\frac{13}{29}\)

\(=\frac{348}{13}\)

248/13

248/13

12:{390:[500-125+35x7]}

=12:{390:620}

=12:39/62

=248/13

a) 6857 + 3444 : 28

=6857 + 123

=6980

b) 80 - [ 130 - ( 75 - 11 ) ]

=80 - [ 130 - 64 ]

=80 - 66

=14

c) 100 : { 2 x [ 52 - ( 35 - 8 ) ]}

=100 : { 2 x [ 52 - 27 ]}

=100 : { 2 x 25 }

=100 : 50

=2

d) 12 : { 390 : [ 500 - ( 125 + 35 + 7 x 30 ) ] }

=12 : { 390 : [ 500 - ( 125 + 35 + 210 ) ] }

=12 : { 390 : [ 500 - 370 ] }

=12 : { 390 : 130 }

=12 : 3

=4

a) 6857 + 3444 : 28 = 6857 +  123 =6980

b) 80 - [ 130 - ( 75 - 11 ) ] = 80 - ( 130 - 64 ) = 80 - 66 = 14

c) 100 : { 2 x [ 52 - ( 35 -  8 ) ] = 100 : [ 2 x ( 52 - 27 ) ] = 100 : (  2 x 25 )= 100 : 50 = 2

d) 12 : { 390 : [ 500 - ( 125 + 35 + 7 x 30 ) ] } = 4

Cái này khi nãy tui đi học thêm gặp nhìu dạng như thế này đấy

a) 6857 + 3444 : 28

=6857 + 123

=6980

b) 80 - [ 130 - ( 75 - 11 ) ]

=80 - [ 130 - 64 ]

=80 - 66

=14

c) 100 : { 2 x [ 52 - ( 35 - 8 ) ]}

=100 : { 2 x [ 52 - 27 ]}

=100 : { 2 x 25 }

=100 : 50

=2

d) 12 : { 390 : [ 500 - ( 125 + 35 + 7 x 30 ) ] }

=12 : { 390 : [ 500 - ( 125 + 35 + 210 ) ] }

=12 : { 390 : [ 500 - 370 ] }

=12 : { 390 : 130 }

=12 : 3

=4

a) 6857 + 3444 : 28

=6857 + 123

=6980

b) 80 - [ 130 - ( 75 - 11 ) ]

=80 - [ 130 - 64 ]

=80 - 66

=14

c) 100 : { 2 x [ 52 - ( 35 - 8 ) ]}

=100 : { 2 x [ 52 - 27 ]}

=100 : { 2 x 25 }

=100 : 50

=2

d) 12 : { 390 : [ 500 - ( 125 + 35 + 7 x 30 ) ] }

=12 : { 390 : [ 500 - ( 125 + 35 + 210 ) ] }

=12 : { 390 : [ 500 - 370 ] }

=12 : { 390 : 130 }

=12 : 3

=4

a) 27.75+25.27-150

= 27.(75+25)-150

= 27.100-150

= 2550

b) 12:{390:[500-(125+75.7)]}

= 12:{390:(500-25.26)}

= 12:{390:[25.(20-26)]}

= 12:(390:(-150)]}

= 12 : \(\dfrac{-13}{5}\)

= \(\dfrac{-60}{13}\)

a)27.75+25.27-150=27.(75+25)-150=27.100-150=2700-150=26850

b)\(12:\left\{390:\left[500-\left(25.5+25.3.7\right)\right]\right\}\)

\(=12:\left\{390:\left[25.20-25.26\right]\right\}\)

\(=12:\left\{3.10.13:\left[-25.6\right]\right\}\)

\(=12:\left(\dfrac{-13}{5}\right)=-12.\dfrac{5}{13}=\dfrac{-60}{13}\)

a,27.75+25.27-150
=27(75+25)-150
=27.100-150
=2700-150
=2550
b)12:{390:[500-(125+75.7)]}
=12:{390:[500-650]}
=12:{390:(-150)}
=12:(-2.6)
=-\(-4\dfrac{8}{13}\)

Câu b chép sai đề rùi kìa 

a)

80 - [ 130 - ( 75 - 11) ]

= 80 - [ 130 - 64 ]

= 80 - 66

= 14

A) \(80-\left[120-\left(75-11\right)\right]=80-\left(120-75+11\right)=80-56=24\)

B) \(12:390:\left[500-\left(125+35+7.30\right)\right]=12:390:\left(500-370\right)=12:390:130=\frac{1}{4225}\)