\(4,7\div0,25+5,3\times4\)

\(=18,8+21,2\)

\(=40\)

\(3\times\left(a-2\right)+150=240\)

\(3\times\left(a-2\right)=90\)

\(a-2=30\)

\(a=32\)

\(\dfrac{1}{9}+a+\dfrac{7}{12}=\dfrac{17}{18}\)

\(\dfrac{1}{9}+a=\dfrac{13}{36}\)

\(a=\dfrac{1}{4}\)

\(\left(\dfrac{1}{2}\times\dfrac{1}{3}+\dfrac{1}{3}\times\dfrac{1}{4}+\dfrac{1}{4}\times\dfrac{1}{5}+\dfrac{1}{5}\times\dfrac{1}{6}+\dfrac{1}{6}\times\dfrac{1}{7}+\dfrac{1}{7}\times\dfrac{1}{8}\right)\times a=\dfrac{9}{16}\)

\(\left(\dfrac{1}{2\times3}+\dfrac{1}{3\times4}+\dfrac{1}{4\times5}+\dfrac{1}{5\times6}+\dfrac{1}{6\times7}+\dfrac{1}{7\times8}\right)\times a=\dfrac{9}{16}\)

\(\left(\dfrac{1}{2}-\dfrac{1}{8}\right)\times a=\dfrac{9}{16}\)

\(\dfrac{3}{8}\times a=\dfrac{9}{16}\)

\(a=\dfrac{3}{2}\)

a)x*5,2:4,5=10,4

x*5,2=10,4*4,5

x*5,2=46,8

x      =46,8:5,2

x      =9

b)5/7*x+2/7*x=2/3

x*(5/7+2/7)=2/3

x*1            =2/3

x                =2/3:1

x                 =2/3

a. 

\(x\times5,2\div4,5=10,4\)

\(x\times5,2=10,4\times4,5\)

\(x\times5,2=46,8\)

\(x=46,8\div5,2\)

\(x=9\)

b.

\(\dfrac{5}{7}\times x+\dfrac{2}{7}\times x=\dfrac{2}{3}\)

\(x\times\left(\dfrac{5}{7}+\dfrac{2}{7}\right)=\dfrac{2}{3}\)

\(x\times1=\dfrac{2}{3}\)

\(x=\dfrac{2}{3}\div1\)

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

\(x\): 2 + \(x\):4 \(\times\) 3 + \(\dfrac{1}{2}\)+ \(x\) + \(x\) : \(\dfrac{2}{3}\) = 1

\(x\) \(\times\) 0,5 + \(x\) \(\times\) 0,25 \(\times\) 3 + 0,5 + \(x\) + \(x\) \(\times\) \(\dfrac{3}{2}\) = 1

\(x\) \(\times\)( 0,5 + 0,25 \(\times\) 3 + 1 + \(\dfrac{3}{2}\)) + 0,5 = 1

\(x\) \(\times\) ( 0,5 + 0,75 + 1 + 1,5) + 0,5 = 1

\(x\) \(\times\) 3,75 + 0,5 = 1

\(x\) \(\times\)3,75 = 1 - 0,5

\(x\) \(\times\) 3,75 = 0,5

\(x\) =0,5 : 3,75

\(x\) = \(\dfrac{2}{15}\)

= 0,75 x 0,25 + 0,75 x 1,25 - 0,75 x 0,5

= 0,75 x ( 0,25 + 1,25 - 0,5 )

= 0,75 x 1

= 0,75

0.75

1) 10/2/5 hay 52/5
2) 90

x / (2/7) = x * 7/2

rồi lấy x làm thừa số chung, rồi tính thừa số kia, rồi tìm x

56x24:12=56x2=112

56x24:3x8=56x24:24=56

63x18:9=63x2=126

`3/5+2/5:x=1 1/10`

`3/5+2/5:x=11/10`

`2/5:x=11/10-3/5=1/2`

`x=2/5:1/2=4/5`

_______________________________________________________

`(x-3/5)xx3/8-5/8=1/6`

`(x-3/5)xx3/8=1/6+5/8`

`(x-3/5)xx3/8=4/24+15/24=19/24`

`x-3/5=19/24:3/8=19/9`

`x=19/9+3/5=122/45`

_______________________________________________________

`1 1/6-5/6:(x+1/4)=1/2`

`7/6-5/6:(x+1/4)=1/2`

`5/6:(x+1/4)=7/6-1/2=2/3`

`x+1/4=5/6:2/3=5/4`

`x=5/4-1/4=4/4=1`

1) (x - 35) - 120 = 0

x - 35 = 120

x = 120 + 35

x = 155

2) 310 - (118 - x) = 217

118 - x = 310 - 217

118 - x = 93

x = 118 - 93

x = 25

3) 156 - (x + 61) = 82

x + 61 = 156 - 82

x + 61 = 74

x = 74 - 61

x = 13

4) 814 - (x - 305) = 712

x - 305 = 814 - 712

x - 305 = 102

x = 102 + 305 = 407

5) 100 - 7 - (x - 5) = 58

x - 5 = 93 - 58

x - 5 = 35

x = 35 + 5 = 40

6) 12(x - 1) : 3 = 4³ + 2³

4(x - 1) = 72

x - 1 = 18

x = 18 + 1 = 19

7) 24 + 5x = 7⁵ : 7³

24 + 5x = 49

5x = 25

x = 25 : 5 = 5

8) 5(x - 1) : 3 = 4³ + 2³

\(\dfrac{5}{3}\left(x-1\right)=72\)

x - 1 = \(\dfrac{216}{5}\)

x = 221/5

9) 5(x - 4)² - 7 = 13

5(x - 4)² = 20

(x - 4)² = 4

\(\Rightarrow\left[{}\begin{matrix}x-4=2\\x-4=-2\end{matrix}\right.\)   \(\Rightarrow\left[{}\begin{matrix}x=6\\x=2\end{matrix}\right.\)

10) (x + 1) + (x + 2) + ... + (x + 30) = 795

=> (x + x + x + ... + x) + (1 + 2 + 3 +...+ 30) = 795 (1)

Đặt A = 1 + 2 + 3 +...+ 30

Số số hạng trong A là: (30 - 1) : 1 + 1 = 30 (số)

Tổng A bằng : (30 + 1).30 : 2 =465

Thay A = 465 vào (1) , ta được:

30x + 465 = 795

=> 30x =330

=> x =11

1: =>x-35=120

=>x=120+35=155

2: =>118-x=310-217=93

=>x=118-93=25

3: =>x+61=156-82=74

=>x=74-61=13

4: =>x-305=814-712=102

=>x=102+305=407

5: =>93-(x-5)=58

=>x-5=35

=>x=40

6: =>4(x-1)=64+8=72

=>x-1=18

=>x=19

7: =>5x+24=49

=>5x=25

=>x=5

8: =>5(x-1):3=4^3+2^3=64+8=72

=>5(x-1)=216

=>x-1=216/5

=>x=221/5

2/2/17 x 1/1/24 x 5/2/5 x 3/7/9 x 2

36/17 x 25/24 x 27/5 x 34/9 x 2

36 x 25 x 27 x 34 x 2/17 x 24 x 5 x 9

1652400/18360=90

1/2/24x5/2/5x2x3/7/9x2x2/17