a) 1/11 + 2/11 + 3/11 + ... + 10/11

= 1 + 2 + 3 + ... + 10 / 11

= (1 + 10).10:2 / 11

= 11.5/11

= 5

b) 1/10×20 + 1/20×30 + 1/30×40 + ... + 1/90×100

= 1/10×10 × (1/1×2 + 1/2×3 + 1/3×4 + ... + 1/9×10)

= 1/100 × (1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + ... + 1/9 - 1/10)

= 1/100 × (1 - 1/10)

= 1/100 × 9/10

= 9/1000

 `A) 1/3 + 1/5 - 1/4 = 20/60 + 12/60 - 15/60 = 17/60`

` B) 7/8 - ( 1/4 + 2/5 ) = 7/8 - 2/4 -2/5 = 5/8-2/8 = 9/40`

` C) 5/11 - ( 3/5 - 6/11 ) = 5/11 - 3/55 = 25/55 - 3/55 = 22/55=2/5 ` 

` D) 5/7 - ( 19/35 - 6/15 ) = 5/7 - 1/7 = 4/7 `

`1/3 + 1/5 -1/4`

`= 5/15 + 3/15 -1/4`

`= 8/15 -1/4`

`=  17/60`

__

`7/8 -(1/4 + 2/5)`

`= 7/8-1/4 - 2/5`

`= 7/8 - 2/8 -2/5`

`= 5/8 -2/5`

`= 9/40`

__

`5/11-(3/5 -6/11)`

`= 5/11 -3/5 +6/11`

`= (5/11 + 6/11)-3/5`

`= 1 -3/5`

`= 5/5-3/5`

`=2/5`

__

`5/7 - ( 19/35 - 6/15)`

`= 5/7 - 19/35 + 6/15`

`= 25/35 -19/35 + 6/15`

`=6/35 +6/15`

`=4/7`

a) 2/9 - (1/20 + 2/9)

= 2/9 - 1/20 - 2/9

= (2/9 - 2/9) - 1/20

= 0 - 1/20

= -1/20

b) -3/14 + 2/13 + (-25/14) + (-15/13)

= (-3/14 - 25/14) + (2/13 - 15/13)

= -2 - 1

= -3

c) -3/11 + 11/8 - 3/8 + (-8/11)

= (-3/11 - 8/11) + (11/8 - 3/8)

= -1 + 1

= 0

d) 3/8 + (-1/4) - (7/12 - 1/6)

= 1/8 - 5/12

= -7/24

e) (1/3 + 12/67 + 13/41) - (79/67 - 28/41)

= 1/3 + 12/67 + 13/41 - 79/67 + 28/41

= 1/3 + (12/67 - 79/67) + (13/41 + 28/41)

= 1/3 - 1 + 1

= 1/3

BÀI 1

a,  \(5\times\frac{-7}{10}=\frac{-35}{10}=\frac{-7}{2}\)

b,  \(\frac{4}{5}\times\frac{-7}{10}=\frac{-28}{50}=\frac{-14}{25}\)

c,  \(\frac{4}{9}+\frac{4}{3}\times\frac{16}{4}=\frac{4}{9}+\frac{16}{3}=\frac{52}{9}\)

d,  \(\frac{11}{22}-\frac{3}{9}\times\frac{14}{21}=\frac{11}{22}-\frac{2}{9}=\frac{55}{198}=\frac{5}{18}\)  

BÀI 2

\(A=\frac{6}{13}\times\frac{5}{7}+\frac{6}{13}\times\frac{2}{7}+\frac{17}{13}\)

\(A=\frac{30}{91}+\frac{12}{91}+\frac{17}{13}\)

\(A=\frac{30}{91}+\frac{12}{91}+\frac{119}{91}\)

\(A=\frac{161}{91}=\frac{23}{13}\)

\(B=\frac{11}{15}\times\frac{4}{11}+\frac{11}{15}\times\frac{5}{11}+\frac{11}{15}\times\frac{2}{11}\)

\(B=\frac{4}{15}+\frac{1}{3}+\frac{2}{15}\)

\(B=\frac{11}{15}\)

\(C=\left(\frac{19}{64}-\frac{33}{22}+\frac{24}{51}\right)\times\left(\frac{1}{5}-\frac{1}{15}-\frac{2}{15}\right)\)

\(C=\frac{-797}{1088}\times0\)

\(C=0\)

\(D=\frac{8}{13}\times\frac{7}{12}+\frac{8}{13}\times\frac{5}{12}-\frac{1}{12}\)

\(D=\frac{14}{39}+\frac{10}{39}-\frac{1}{12}\)

\(D=\frac{83}{156}\)

bạn biết câu náy không (24 + 11) . {546 - [14 . (64 - 2^{3}3) : 2]} =

ai cứu với ạ

ko 

có chết đâu mà phải cứu

mk đang cần gấp người giải ai thấy bài này giải giúp mk nha 

a.17/60

b.9/40

c.2/5

a)

1/3 + 1/5 - 1/4

= 8/15 - 1/4

= 17/80

b)

7/8 - (1/4 + 2/5)

= 7/8 - 13/20

= 9/40

c) 5/11 - (3/5 - 6/11)

= 5/11 - 2/55

= 2/5

a: \(\dfrac{11}{4}+\left(-\dfrac{3}{5}+\dfrac{1}{3}\right):\dfrac{-4}{9}\)

\(=\dfrac{11}{4}+\dfrac{-9+5}{15}\cdot\dfrac{9}{-4}\)

\(=\dfrac{11}{4}+\dfrac{-4}{15}\cdot\dfrac{9}{-4}\)

\(=\dfrac{11}{4}+\dfrac{3}{5}=\dfrac{55+12}{20}=\dfrac{67}{20}\)

b: \(\dfrac{2}{6}-\left(-\dfrac{3}{3}+\dfrac{4}{7}\right):\dfrac{-9}{5}\)

\(=\dfrac{2}{6}-\left(-1+\dfrac{4}{7}\right)\cdot\dfrac{-5}{9}\)

\(=\dfrac{2}{6}-\dfrac{-3}{7}\cdot\dfrac{-5}{9}\)

\(=\dfrac{1}{3}-\dfrac{15}{63}\)

\(=\dfrac{6}{63}=\dfrac{2}{21}\)

c: \(21-\dfrac{15}{4}:\left(\dfrac{3}{8}-\dfrac{1}{6}\right)\)

\(=21-\dfrac{15}{4}:\dfrac{3\cdot3-4}{24}\)

\(=21-\dfrac{15}{4}\cdot\dfrac{24}{5}\)

\(=21-3\cdot6=3\)

\(a.\dfrac{11}{4}+\left(-\dfrac{3}{5}+\dfrac{1}{3}\right):-\dfrac{4}{9}\)

\(=\dfrac{11}{4}+\left(-\dfrac{4}{15}\right):-\dfrac{4}{9}\)

\(=\dfrac{11}{4}+\dfrac{3}{5}=\dfrac{67}{20}\)

\(b.\dfrac{2}{6}-\left(-\dfrac{3}{3}+\dfrac{4}{7}\right):-\dfrac{9}{5}\)

\(=\dfrac{2}{6}-\left(-\dfrac{3}{7}\right):-\dfrac{9}{5}\)

\(=\dfrac{2}{6}-\dfrac{5}{21}=\dfrac{2}{21}\)

\(c.21-\dfrac{15}{4}:\left(\dfrac{3}{8}-\dfrac{1}{6}\right)\)

\(=21-\dfrac{15}{4}:\dfrac{5}{24}\)

\(=21-18=3\)