A=[(1+9)+(3+7)+(5+15)+(11+13)].2

A=[10+10+20+24].2

A=64.2

A=128

B=(17+23)+(19+21)+(23+27)+(25+29)

B=40+40+50+54

B=tự tính

A=(1+9)+(3+7)+(5+15)+(7+13)+(11.2)

A=10+10+10+10+22

A=40+22

A=62

mình làm câu A thôi nhé

1. Tính giá trị biểu thức:

a) (2/5 x 25/29) + (3/5 x 25/29)
= (50/145) + (75/145)
= 125/145

b) (5/2 x 3/7) - (3/14 : 6/7)
= 15/14 - (3/14 x 7/6)
= 15/14 - 1/2
= (30/28) - (14/28)
= 16/28
= 4/7

c) (15/4 : 5/12) - (6/5 : 11/15)
= (15/4 x 12/5) - (6/5 x 15/11)
= 180/20 - 90/55
= 9 - 18/11
= (99/11) - (18/11)
= 81/11
= 7 4/11

2. Tính giá trị biểu thức:

a) (2/3) + (20/21 x 3/2 x 7/5)
= 2/3 + (60/210)
= 2/3 + 2/7
= (14/21) + (6/21)
= 20/21

b) (5/17 x 21/32 x 47/24 x 0)
= 0

c) (11/3 x 26/7) - (26/7 x 8/3)
= (286/21) - (208/21)
= 78/21
= 3 9/21
= 3 3/7

3. Tìm x:

a) (25/8) : x = 5/16
=> (25/8) x (16/5) = x
=> 4 = x

b) x + (7/15) = 6/15
=> x = (6/15) - (7/15)
=> x = -1/15

c) x : (28/49) = 7/12
=> x x (49/28) = 7/12
=> x = (7/12) x (28/49)
=> x = 1/2

4. Tìm x:

a) 6 x x = (5/8) : (3/4)
=> 6x = (5/8) x (4/3)
=> 6x = 20/24
=> 6x = 5/6
=> x = (5/6) / 6
=> x = 5/36

câu,b,không,đủ,thông,tin,nhan,bạn.

a) Ta có:

C = 5/18 + 8/19 - 7/21 + (-10/36 + 11/19 + 1/3) - 5/8

C = 5/18 + 8/19 - 1/3 - 5/18 + 11/19 + 1/3 - 5/8

C = (5/18 - 5/18) + (8/19 + 11/19) - (1/3  - 1/3) - 5/8

C = 1 - 5/8

c = 3/8

b) F = 15/14 - (17/23 - 80/87 + 5/4) + (17/23 - 15/14 + 1/4)

F = 15/14 - 17/23 + 80/87 - 5/4 + 17/23 - 15/14 + 1/4

F = (15/14 - 15/14) - (17/23 - 17/23) + 80/87 - (5/4 - 1/4)

F = 80/87 - 1

F = -7/87

c) G = 1/25 - 4/27 + (-23/27 + -1/25 - 5/43) + 5/43 - 4/7

G = 1/25 - 4/27 - 23/27 - 1/25 - 5/43 + 5/43 - 4/7

G = (1/25 - 1/25) - (4/27 + 23/27) - (5/43 - 5/43) - 4/7

G = -1 - 4/7 = -11/7

a. \(\left(-37\right)+14+26+37\)

\(=\left[\left(-37\right)+37\right]+\left(14+26\right)\)

\(=0+40\)

\(=40\)

b. \(\left(-24\right)+6+10+24\)

\(=\left[\left(-24\right)+24\right]+6+10\)

\(=0+6+10\)

\(=16\)

c. \(15+23+\left(-25\right)+\left(-23\right)\)

\(=\left[\left(-25\right)+15\right]+\left[\left(-23\right)+23\right]\)

\(=-10+0\)

\(=-10\)

các câu khác bn tự lm

d. \(35\cdot18-5\cdot7\cdot28\)

\(=35\cdot18-35\cdot28\)

\(=35\cdot\left(18-28\right)\)

\(=35\cdot\left(-10\right)\)

\(=-350\)

câu e, f, g bn tự lm

a,\(\frac{21}{25}.\frac{11}{9}.\frac{5}{7}=\frac{21.11.5}{25.9.7}=\frac{3.7.11.5}{5^2.3^2.7}=\frac{11}{5.3}=\frac{11}{15}\)

b,\(\frac{5}{23}.\frac{17}{26}+\frac{5}{23}.\frac{9}{26}=\frac{5}{23}.\left(\frac{17}{26}+\frac{9}{26}\right)=\frac{5}{23}.1=\frac{5}{23}\)

c, \(\left(\frac{3}{29}-\frac{1}{5}\right).\frac{29}{3}=\frac{3}{29}.\frac{29}{3}-\frac{1}{5}.\frac{29}{3}=1-\frac{29}{15}=-\frac{14}{15}\)

a , \(\frac{21}{25}\times\frac{11}{9}\times\frac{5}{7}\) 

\(=\frac{21\times11\times5}{25\times9\times7}\)

\(=\frac{3\times7\times11\times5}{5\times5\times3\times3\times7}\) 

\(=\frac{11}{5\times3}\) 

\(=\frac{11}{15}\) 

b ,   \(\frac{5}{23}\times\frac{17}{26}+\frac{5}{23}\times\frac{9}{26}\) 

\(=\frac{5}{23}\times\left(\frac{17}{26}+\frac{9}{26}\right)\)

\(=\frac{5}{23}\times\frac{26}{26}\) 

\(=\frac{5}{23}\times1\) 

\(=\frac{5}{23}\) 

c , \(\left(\frac{3}{29}-\frac{1}{5}\right)\times\frac{29}{3}\) 

\(=\frac{3}{29}\times\frac{29}{3}-\frac{1}{5}\times\frac{29}{3}\) 

\(=1-\frac{29}{15}\) 

\(A=\left(4+\frac{1}{5}\right).\frac{19}{8}+\left(2+\frac{5}{8}\right).\frac{21}{5}\)                                                                                                                                                     =\(\frac{21}{5}.\frac{19}{8}+\frac{21}{8}.\frac{21}{5}\)                                                                                                                                                                             =\(\frac{21}{5}.\left(\frac{19}{8}+\frac{21}{8}\right)\)                                                                                                                                                                           = \(\frac{21}{5}.5\) =21                                                                                                                                                                                       \(B=\frac{25}{2}.\left(3+\frac{2}{7}\right)-\frac{23}{7}.\left(5+\frac{1}{2}\right)\)                                                                                                                                            =\(\frac{25}{2}.\frac{23}{7}-\frac{23}{7}.\frac{11}{2}\)                                                                                                                                                                       =\(\frac{23}{7}.\left(\frac{25}{2}-\frac{11}{2}\right)\)                                                                                                                                                                          =\(\frac{23}{7}.7=23\)

c=39/64

d=913/105

3) C thiếu đề

4) \(D=\frac{1}{9}-\left|\frac{-5}{23}\right|-\left(\frac{-5}{23}+\frac{1}{9}+\frac{25}{7}\right)+\frac{50}{4}-\frac{7}{30}\)

\(D=\frac{1}{9}-\frac{5}{23}+\frac{5}{23}-\frac{1}{9}-\frac{25}{7}+\frac{50}{4}-\frac{7}{30}\)

\(D=\frac{1}{9}-\frac{1}{9}-\frac{5}{23}+\frac{5}{23}+\frac{-25}{7}+\frac{50}{4}-\frac{7}{30}\)

\(D=0+0+\frac{125}{14}-\frac{7}{30}\)

\(D=\frac{913}{105}\)

B = 21 x 23 + 21 x 29 + 147 x 7

B = 21 x 23 + 21 x 29 + 21 x 7 x 7

B = 21 x 23 + 21 x 29 + 21 x 49

B = 21 x ( 23 + 29 + 49 )

B = 21 x 101

B = 2121

B = 21 x 23 + 21 x 29 + 147 x 7

B = 21 x 23 + 21 x 29 + 21 x 7 x 7

B = 21 x 23 + 21 x 29 + 21 x 49

B = 21 x(23+29+49)

B = 21 x 101

B = 21 x(100+1)

B = 21 x 100 + 21 x 1

B = 2100 + 21

B = 2121

A = (4+\(\frac{1}{5}\)) . \(\frac{18}{19}\)+ (2+\(\frac{8}{5}\)) . \(\frac{21}{5}\)

A= \(\frac{21}{5}\).18/19 + 18/5 . 21/5

A= 21/5 (18/19 + 18/5)

A= 21/5 . 432/95

A= 9288/95

b= 25/2. (3+2/7) - 23/7. (5 + 1/2)

b= 25/2 . 23/7 - 23/7 . 11/2

b= 23/7 (25/2 -11/2)

b=23/7 . 7

b= 23