( 5/7 - y ) * 14/5 = 7/10 + 1/2

( 5/7 - y ) x 14/5 = 6/5

 5/7 - y  = 6/5 : 14/5

5/7 - y = 3/7

y = 5/7 - 3/7

y = 2/7

bằng 2/7

(5/7-y)x14/5=6/5

5/7-y=6/5:14/5

5/7-y=3/7

y=5/7-3/7

x=2/7

Ta có : \(\left(\frac{5}{7}-y\right)\times\frac{14}{5}=\frac{7}{10}+\frac{1}{2}\)

\(\Rightarrow\left(\frac{5}{7}-y\right)\times\frac{14}{5}=\frac{12}{10}=\frac{6}{5}\)

\(\Rightarrow\left(\frac{5}{7}-y\right)=\frac{6}{5}:\frac{14}{5}\)

\(\Rightarrow\left(\frac{5}{7}-y\right)=\frac{30}{70}=\frac{3}{7}\)

\(y=\frac{5}{7}-\frac{3}{7}=\frac{2}{7}\)

violympic đúng ko nè bạn

chờ chút để mik giải nhé

\(\left(\frac{5}{7}-y\right).\frac{14}{5}=\frac{7}{10}+\frac{1}{2}\)

\(\left(\frac{5}{7}-y\right).\frac{14}{5}=\frac{6}{5}\)

\(\frac{5}{7}-y=\frac{6}{5}:\frac{14}{5}\)

\(\frac{5}{7}-y=\frac{3}{7}\)

\(y=\frac{5}{7}-\frac{3}{7}\)

\(y=\frac{2}{7}\)

2/7

k cho minh

\(\left(\frac{5}{7}-y\right)\times\frac{14}{5}=\frac{7}{10}+\frac{1}{2}\)

\(\left(\frac{5}{7}-y\right)\times\frac{14}{5}=\frac{6}{5}\)

\(\frac{5}{7}-y=\frac{6}{5}:\frac{14}{5}\)

\(\frac{5}{7}-y=\frac{3}{7}\)

\(y=\frac{5}{7}-\frac{3}{7}\)

\(y=\frac{2}{7}\)

a) y = 5/14 : 6/7

y = 5/12 

vậy y = 5/12

b) y = 4/9 x 2/3 

y = 8/27 

vậy t = 8/27

c) y = 1/2 - 3/10 

y = 1/5

vậy y = 1/5

d) y = 5/6 - 1/3

y = 1/2

vậy y = 1/2

`a, 2/3 + 1/5 . 10/7`

`= 2/3 + 10/35`

`=2/3 +2/7`

`=14/21 + 6/21`

`=20/21`

`b, 2/7 + 5/7 . 14/25`

`=  2/7 +2/5`

`= 10/35+14/35`

`= 24/35`

`c, 7/12 - 27/7 . 1/18`

`= 7/12 - 3/14`

`= 31/84`

`d, 3/10 . (-5/6) - 1/8`

`= -1/4 -1/8`

`= -2/8 -1/8`

`= -3/8`

a)

\(\dfrac{2}{3}+\dfrac{1}{5}.\dfrac{10}{7}\)

\(=\dfrac{2}{3}+\dfrac{2}{7}\)

\(=\dfrac{14}{21}+\dfrac{6}{21}\)

\(=\dfrac{20}{21}\)

b)

\(\dfrac{2}{7}+\dfrac{5}{7}.\dfrac{14}{25}\)

\(=\dfrac{2}{7}+\dfrac{2}{5}\)

\(=\dfrac{10}{35}+\dfrac{14}{35}\)

\(=\dfrac{24}{35}\)

c)

\(\dfrac{7}{12}-\dfrac{27}{7}.\dfrac{1}{18}\)

\(=\dfrac{7}{12}-\dfrac{3}{14}\)

\(=\dfrac{98}{168}-\dfrac{36}{168}\)

\(=\dfrac{31}{84}\)

d)

\(\dfrac{3}{10}.\left(-\dfrac{5}{6}\right)-\dfrac{1}{8}\)

\(=-\dfrac{1}{4}-\dfrac{1}{8}\)

\(=-\dfrac{2}{8}-\dfrac{1}{8}\)

\(=\dfrac{-3}{8}\)

(\(\frac{5}{7}-y\)) x \(\frac{14}{5}=\frac{6}{5}\)

\(\frac{5}{7}-y\)            = \(\frac{6}{5}:\frac{14}{5}\)

\(\frac{5}{7}-y\)             = \(\frac{3}{7}\)

            y                 = \(\frac{5}{7}-\frac{3}{7}\)

           y                  = \(\frac{2}{7}\)

\(\left(\frac{5}{7}-y\right)\cdot\frac{14}{5}=\frac{7}{10}+\frac{1}{2}\)

\(\Leftrightarrow\left(\frac{5}{7}-y\right)\cdot\frac{14}{5}=\frac{7}{10}+\frac{5}{10}\)

\(\Leftrightarrow\left(\frac{5}{7}-y\right)\cdot\frac{14}{5}=\frac{6}{5}\)

\(\Leftrightarrow\frac{5}{7}-y=\frac{6}{5}\div\frac{14}{5}\)

\(\Leftrightarrow\frac{5}{7}-y=\frac{3}{7}\)

\(\Rightarrow y=\frac{5}{7}-\frac{3}{7}=\frac{2}{7}\)

bạn viết cái này nó dễ hơn đó 

ta có 

\(\frac{2.6.10+6.10.14+..+194.198.202}{1.3.5+3.5.7+..+97.99.101}=\frac{8.1.3.5+8.3.5.7+..+8.97.99.101}{1.3.5+3.5.7+..+97.99.101}\)

\(=\frac{8.\left(1.3.5+3.5.7+..+97.99.101\right)}{1.3.5+3.5.7+..+97.99.101}=8\)