a) (x.7 + 8) : 5 = 10

x.7 + 8 = 10.5

x.7 + 8 = 50

x.7 = 50 - 8

x.7 = 42

x = 42 : 7

x = 6

b) (x + 5).19 : 13 = 57

(x + 5).19 = 57 . 13

(x + 5).19 = 741

x + 5 = 741 : 19

x + 5 = 39

x = 39 - 5

x = 34

c) 4.(36 - 4.x) = 64

36 - 4x = 64 : 4

36 - 4x = 16

4x = 36 - 16

4x = 20

x = 20 : 4

x = 5

d) 7,6 : 19 . x = 3,2

0,4 . x = 3,2

x = 3,2 : 0,4

x = 8

e) (x : 2 + 50) : 5 = 12

x : 2 + 50 = 12 . 5

x : 2 + 50 = 60

x : 2 = 60 - 50

x : 2 = 10

x = 10 . 2

x = 20

g) 280 : (17 + 3.x) = 4

17 + 3x = 280 : 4

17 + 3x = 70

3x = 70 - 17

3x = 53

x = 53/3

h) 6.(28 - 8.x) = 72

28 - 8x = 72 : 6

28 - 8x = 12

8x = 28 - 12

8x = 16

x = 16 : 8

x = 2

i) (x - 15) : 3 : 12 = 6

(x - 15) : 3 = 6 . 12

(x - 15) : 3 = 72

x - 15 = 72 . 3

x - 15 = 216

x = 216 + 15

x = 231

1> a) \(\frac{5}{7}x4:\frac{5}{9}=\frac{5}{7}:\frac{5}{9}x4=\frac{5}{7}x\frac{9}{5}x4=\frac{9}{7}x4=\frac{9x4}{7}=\frac{36}{7}\)

\(b,8x\frac{2}{3}:\frac{1}{2}=8x\frac{2}{3}x\frac{2}{1}=8x2x\frac{2}{3}=16x\frac{2}{3}=\frac{32}{3}\)

\(c,6:\frac{3}{5}-\frac{7}{6}x\frac{6}{7}=6x\frac{5}{3}-1=10-1=9\)

\(\frac{21}{5}x\frac{10}{11}+\frac{57}{11}=\frac{42}{11}+\frac{57}{11}=\frac{99}{11}=9\)

2) a) \(\frac{35}{9}:x=\frac{35}{6}\)

\(x=\frac{35}{9}:\frac{35}{6}\)

\(x=\frac{35}{9}x\frac{6}{35}\)

\(x=\frac{2}{3}\)

b) \(\left(\frac{1}{1x2}+\frac{1}{2x3}+\frac{1}{3x4}+\frac{1}{4x5}+\frac{1}{5x6}\right)x10-X=0\)

\(\left(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+.....+\frac{1}{5}-\frac{1}{6}\right)x10-X=0\)

\(\left(\frac{1}{1}-\frac{1}{6}\right)x10-X=10\)

\(\frac{5}{6}x10-X=0\)

\(X=\frac{5}{6}x10=\frac{25}{3}\)

Đúng nha !!!!

1/a/\(\frac{5}{7}\cdot4:\frac{5}{9}=\frac{20}{7}:\frac{5}{9}=\frac{20}{7}\cdot\frac{9}{5}=\frac{36}{7}\)

b/\(8\cdot\frac{2}{3}:\frac{1}{2}=\frac{16}{3}:\frac{1}{2}=\frac{16}{3}\cdot\frac{2}{1}=\frac{32}{3}\)

c/\(6:\frac{3}{5}-\frac{7}{6}\cdot\frac{6}{7}=6\cdot\frac{5}{3}-1=10-1=9\)

2/a/\(\frac{35}{9}:x=\frac{35}{6}\)

\(x=\frac{35}{9}:\frac{35}{6}=\frac{35}{9}\cdot\frac{6}{35}\)

\(x=\frac{2}{3}\)

b/\(\left(\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+\frac{1}{4\cdot5}+\frac{1}{5\cdot6}\right)\cdot10-x=0\)

\(\left(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}\right)\cdot10-x=0\)

\(\left(\frac{30}{60}+\frac{10}{60}+\frac{5}{60}+\frac{2}{30}\right)\cdot10-x=0\)

\(\frac{47}{60}\cdot10-x=0\)

\(\frac{47}{6}-x=0\)

\(x=\frac{47}{6}-0\)

\(x=\frac{47}{6}\)

xs

\(a,2.\left(x-5\right)-3.\left(x+7\right)=14\)

            \(2x-10-3x-21=14\)

                                 \(-x-31=14\)

                                                \(x=-31-14\)

                                                \(x=-45\)

\(b,5.\left(x-6\right)-2\left(x+3\right)=12\)

             \(5x-30-2x-6=12\)

                                \(3x-36=12\)

                                           \(3x=12+36\)

                                           \(3x=48\)

                                              \(x=16\)

\(c,-5.\left(2-x\right)+4.\left(x-3\right)=10.x-15\)

              \(-10+5x+4x-12=10x-15\)

                                    \(-6x-22=10x-15\)

                                  \(-6x-10x=-15+22\)

                                             \(-16x=7\)

                                                      \(x=-\frac{7}{16}\)

Câu d , e f tương tự nha

bạn làm rất   đúng ,cảm ơn bn nhìu

dễ mà bn

A. 5(x-11) + 4(x-3) =10
<=>5x -55 + 4x -12 =10
<=>9x -67 =10
<=>9x =10+67 =77
<=>x =77 : 9 =77/9
B.21 - 5 ( x-7) = 2-3(x-5)
<=>21-5x+35 = 2 - 3x +15
<=>-5x + 56 = -3x + 17
<=>-5x +3x=17-56=-39
<=> -2x =-39
<=> x = -39 : -2 =39/2
C.3(2x-1)-7(x+4)=8-9x
<=>6x -4 -7x-28=-9x+8
<=>-x + 9x = 8+4+28=40
<=> 8x = 40
<=> x = 40:8=5
D. l 4-x l =11
<=>\(\orbr{\begin{cases}4-x=11\\4-x=-11\end{cases}}\)<=> \(\orbr{\begin{cases}x=-7\\x=15\end{cases}}\)
E. 5-3 l x+2 l = -28
<=> 3 l x+2 L = -28 -5 =-33
<=> l x+2 l = -33 :3 =11
<=>\(\orbr{\begin{cases}x+2=11\\x+2=-11\end{cases}}\)<=> \(\orbr{\begin{cases}x=9\\-13\end{cases}}\)
 T I C K mk nhé!!!^_^

a: 2h15'-48p=135p-48p=87p

b: =3 năm 16 tháng-2 năm 10 tháng=1 năm 6 tháng

c: =520 năm-335 năm=185 năm

d: =5h12'-2h5'=3h7'

e: =96p200s=99p20s

f: =48h120p=50h

g: =105p147s=107p27s

h: =60 ngày 75h

=63 ngày 3 giờ

i: 28 ngày 36 giờ:4

=7 ngày 9 giờ

j:

24,12p:6=4,02p

1/2×(2×x-3)+105/2=-137/2

1/2×(2×x-3)=-137/2-105/2

1/2×(2×x-3)=-242/2

2×x-3=-242/2:1/2

2×x-3=-242

2.x=(-242)+3

2.x=239

x=239:2

x=239/2

A,-12×25-25×75-25×13

=[(-12)-75-13].25

=(-100).25

-2500

B,-50/7×49/10-35/2×-10/7+ -25/3× -9/5

=(-35)-(-25)+(-13)

=-23

C,-354+265-156+125

=[(-354)-156]+(265+125)

=(-510)+277

=-233

D,-74+40-50+16-35

=(-74)+40+(-50)+16+(-35)

=[(-74)+(-35)]+[40+(-50)+16]

=(-109)+26

=-83

E,-2/3×4/5+-4/5×4/3-0,125

=-2/3.4/5+4/5.(-4/3)-0,125

=4/5.[-2/3+(-4/3)]-0,125

=4/5.(-2)-0,125

=-8/5-0,125

=(-1,6)+(-0,125)

=-1,725

a) 3/4 + -1/8 = 5/8

b)-5/12 + -7/24 = -9/8

c) 4/21 - -5/28 = 31/84

d) 1 + -7/28 = 3/4

e) -4/3 - 17/6= -25/6

f) 1/3 - ( 1/2 +1/8 )= -7/24

g)1/21 - ( 1/7 - 1/3 ) = 5/21

h)1/2 - 1/4 + 1/13 + 1/8= 47/104

a) x - 1/10 = 1/15

x=1/15+1/10

b) -4/21 - x = -3/7

c) x + 1/2 = 3/4 - (-1/2)

x+1/2= 5/4

x= 5/4-1/2

x=3/4

Vay x=3/4

d) 4/7 - x = 1/3 - (-2/3)

a) \(\Rightarrow5\left(x-10\right)=10\)

\(\Rightarrow x-10=2\Rightarrow x=12\)

b) \(\Rightarrow3\left(70-x\right)+5=92\)

\(\Rightarrow3\left(70-x\right)=87\)

\(\Rightarrow70-x=29\Rightarrow x=41\)

c) \(\Rightarrow230+\left[16+\left(x-5\right)\right]=315\)

\(\Rightarrow11+x=85\Rightarrow x=74\)

d) \(\Rightarrow707:\left(2^x-5+74\right)=7\)

\(\Rightarrow2^x-5+74=101\Rightarrow2^x-5=27\)

\(\Rightarrow2^x=32\Rightarrow x=5\)

a) \(\dfrac{1}{2}-\left(x+\dfrac{1}{3}\right)=\dfrac{5}{6}\)

\(\Rightarrow x+\dfrac{1}{3}=\dfrac{1}{2}-\dfrac{5}{6}\)

\(\Rightarrow x+\dfrac{1}{3}=\dfrac{-1}{3}\)

\(\Rightarrow x=\dfrac{-1}{3}-\dfrac{1}{3}\)

\(\Rightarrow x=\dfrac{-2}{3}\)

b)\(\dfrac{3}{4}-\left(x+\dfrac{1}{2}\right)=\dfrac{4}{5}\)

\(\Rightarrow x+\dfrac{1}{2}=\dfrac{3}{4}-\dfrac{4}{5}\)

\(\Rightarrow x+\dfrac{1}{2}=\dfrac{-1}{20}\)

\(\Rightarrow x=\dfrac{-1}{20}-\dfrac{1}{2}\)

\(\Rightarrow x=\dfrac{-11}{20}\)

c) \(\dfrac{3}{35}-\left(\dfrac{3}{5}+x\right)=\dfrac{2}{7}\)

\(\Rightarrow\dfrac{3}{5}+x=\dfrac{3}{35}-\dfrac{2}{7}\)

\(\Rightarrow\dfrac{3}{5}+x=\dfrac{-1}{5}\)

\(\Rightarrow x=\dfrac{-1}{5}-\dfrac{3}{5}\)

\(\Rightarrow x=\dfrac{-4}{5}\)

d)\(\dfrac{2}{3}.x=\dfrac{4}{27}\)

\(\Rightarrow x=\dfrac{4}{27}:\dfrac{2}{3}\)

\(\Rightarrow x=\dfrac{2}{9}\)

e) \(\dfrac{-3}{5}.x=\dfrac{21}{10}\)

\(\Rightarrow x=\dfrac{21}{10}:\dfrac{-3}{5}\)

\(\Rightarrow x=\dfrac{-7}{2}\)