a: \(=\dfrac{5}{4}\cdot\dfrac{2}{5}\cdot\dfrac{17}{21}\cdot\dfrac{7}{34}=\dfrac{1}{2}\cdot\dfrac{1}{2}\cdot\dfrac{1}{3}=\dfrac{1}{12}\)

b: =>0,5^x(0,5+1)=1,5

=>0,5^x=1

=>x=0

c: =>x*0,05-0,25*x=-1,2

=>-0,3*x=-1,2

=>x=4

d: =>x-1=1 hoặc x-1=-1

=>x=0 hoặc x=2

e: =5+4=9

`Nxx20%+1/4xxN+Nxx1,25+89=123`

`Nxx0,2+0,25xxN+Nxx1,25=123-89`

`Nxx(0,2+0,25+1,25)=34`

`Nxx1,7=34`

`N=34:1,7=20`

Một xe máy đi với vận tốc 28,6 km/h quãng đường đi được của xe máy trong 3 giờ là

8,75 x X + 0,75 + 1,25 x X + 0,25 = 20 + 0,25 + 0,75

8,75 x X + 0,75 + 1,25 x X + 0,25 = 20 + 1

8,75 x X + 0,75 + 1,25 x X + 0,25 = 21

( 8,75 + 1,25 ) x X + ( 0,75 + 0,25) = 21

10 x X + 1 = 21

10 x X       = 21 - 1

10 x X       = 20

       X       =  20 : 10

       X       = 2

tk nha

8,75x X+0,75+1,25x X +0,25=20+1/4+0,75

8,75x X +0,75+1,25x X +0,25=21

(8,75+0,25)xX+0,75=21

9xX+0,75=21

9xX=21-0,75

9xX=20,25

X=20,25:9

X=2,25

mk nhanh nhất tk nha

8,75 x X + 0.75 +1,25 x X + 0,25 = 20 + 1/4 + 0,75

=> 8,75x + 0,75 + 1,25x + 0,25 = 20 + 1/4 + 0,75

=> 8,75x + 1,25x = 20 

=> 10x = 20

=> x = 2

Vậy x là 2

a; - \(\dfrac{10}{13}\) + \(\dfrac{5}{17}\) - \(\dfrac{3}{13}\) + \(\dfrac{12}{17}\) - \(\dfrac{11}{20}\)

= - (\(\dfrac{10}{13}\) + \(\dfrac{3}{13}\)) + (\(\dfrac{5}{17}\) + \(\dfrac{12}{17}\)) - \(\dfrac{11}{20}\)

= - 1 + 1  - \(\dfrac{11}{20}\)

=   0 - \(\dfrac{11}{20}\)

= - \(\dfrac{11}{20}\)

b; \(\dfrac{3}{4}\) + \(\dfrac{-5}{6}\) - \(\dfrac{11}{-12}\)

= \(\dfrac{9}{12}\) - \(\dfrac{10}{12}\) + \(\dfrac{11}{12}\)

= \(\dfrac{10}{12}\)

= \(\dfrac{5}{6}\)

c; [13.\(\dfrac{4}{9}\) + 2.\(\dfrac{1}{9}\)] - 3.\(\dfrac{4}{9}\)

= [\(\dfrac{52}{9}\) + \(\dfrac{2}{9}\)] - \(\dfrac{4}{3}\)

= \(\dfrac{54}{9}\) - \(\dfrac{4}{3}\)

= \(\dfrac{14}{3}\)

d; 1,25 : \(\dfrac{15}{20}\) + [25% - \(\dfrac{5}{6}\)] : 4.\(\dfrac{2}{3}\)

= 1,25  x \(\dfrac{20}{15}\) + [\(\dfrac{1}{4}\) - \(\dfrac{5}{6}\)] : 4.\(\dfrac{2}{3}\)

=  \(\dfrac{5}{3}\) - \(\dfrac{7}{12}\) : 4 x \(\dfrac{2}{3}\)

= \(\dfrac{5}{3}\) - \(\dfrac{7}{48}\).\(\dfrac{2}{3}\)

= \(\dfrac{5}{3}\) - \(\dfrac{7}{72}\)

= \(\dfrac{113}{72}\)

Nx20%+1/4xN+1,25+89=123

Nx1/5+1/4xN+90,25=123

Nx(1/5+1/4)=123-90,25

Nx9/20=32,75

N=32,75x9/20

N=655/9

a , 5*x*8.3=20.75

5*x=20.75:8.3

5*x=2.5

x=2.5:5

x=0.5

b : làm tương tự nha bn

a, 5 nhân x bằng 20,75 : 8,3                                                            

    5 nhân x bằng2,5

                x bằng 2,5:5

                x bằng 0,5

a) 5*x=20, 75:8,3

    5*x=2,5

    x=2,5:5

    x=0.5

k cho mình nhé bạn thân mến!!!

\(\frac{4}{5}x\frac{1}{20\%}+0,08=4,08\)

\(2001:25-1999:25=0,08\)

\(75x1,25=93,75\)

\(56x2,5x400=56000\)

\(1600:1,25=1280\)

\(k\)\(nha♥♥♥♥\)

bạn trình bày lun được k ?

4/5 x 1/20% + 0,08 = 4 + 0,08

                               = 4,08

2001 : 25 - 1999 : 25 = 80,04 - 79,96 

                                  = 0,08

75 x 1,25 = 93,75

56 x 2,5 x 400 = 56 x 1000

                       = 56 000

1600 : 1,25 = 1280

xong rồi đó                 

\(=\left(\dfrac{1}{2}-\dfrac{6}{5}\right):\dfrac{21}{20}-\dfrac{25}{4}+\dfrac{1}{2}\)

\(=\dfrac{-7}{10}\cdot\dfrac{20}{21}-\dfrac{25}{4}+\dfrac{2}{4}\)

\(=\dfrac{-2}{3}-\dfrac{23}{4}=\dfrac{-8-69}{12}=\dfrac{-77}{12}\)

\(\left(\sqrt{\dfrac{1}{4}}-1,2\right):1\dfrac{1}{20}-\left(-\dfrac{5}{2}\right)^2+\left|1,25-\dfrac{3}{4}\right|\)

\(=-\dfrac{7}{10}:\dfrac{21}{20}-\dfrac{25}{4}+\left|\dfrac{1}{2}\right|\)

\(=-\dfrac{7}{10}.\dfrac{20}{21}-\dfrac{25}{4}+\dfrac{1}{2}\)

\(=-\dfrac{2}{3}-\dfrac{25}{4}+\dfrac{1}{2}\)

\(=-\dfrac{77}{12}\)