=3/5*\((\)2/7+4/7\()\)+2/5

=3/5*6/7+2/5

=18/35+2/5

=32/35

\(=\dfrac{2}{5}\cdot\dfrac{7}{3}\cdot\dfrac{3}{7}\cdot\dfrac{5}{2}+2020=1+2020=2021\)

\(\dfrac{2}{5}\times\dfrac{4}{7}+\dfrac{4}{7}\times\dfrac{3}{5}=\left(\dfrac{2}{5}+\dfrac{3}{5}\right)\times\dfrac{4}{7}=1\times\dfrac{4}{7}=\dfrac{4}{7}\)

`2/5 xx 4/7 + 3/5 xx 4/7`

`= 4/7 xx (2/5 + 3/5)`

`= 4/7 xx 1`

`= 4/7`

\(\dfrac{2}{5}\times\dfrac{4}{7}+\dfrac{3}{5}\times\dfrac{4}{7}=\left(\dfrac{2}{5}+\dfrac{3}{5}\right)\times\dfrac{4}{7}=\dfrac{5}{5}\times\dfrac{4}{7}=1\times\dfrac{4}{7}=\dfrac{4}{7}\)

=7/10(3+5+2)

=7/10*10

=7

3 x 7/10 + 7/10 x 5 + 2 x 7/10

= 7/10 x (3 + 5 + 2)

= 7/10 x 10

= 7

\(\dfrac{7}{10}\times\left(3+5+2\right)=\dfrac{7}{10}\times10=\dfrac{70}{10}=7\)

`3xx7/10+7/10xx5+2xx7/10`

`=7/10xx(3+5+2)`

`=7/10xx10`

`=7`

a) \(19\times\left(52+38\right)-9\times\left(52+38\right)=\)

\(=\)     \(19\times90-9\times90\) 

\(=90\times\left(19-9\right)\) 

\(=90\times10\) 

\(=900\) 

b) \(\dfrac{2}{5}\div\dfrac{3}{7}\times\dfrac{3}{7}\div\dfrac{2}{5}+2019=\)

\(=\left(\dfrac{2}{5}\div\dfrac{2}{5}\right)\times\left(\dfrac{3}{7}\div\dfrac{3}{7}\right)+2019\) 

\(=1\times1+2019\) 

\(=2019\)

lx

Uả cái j zị

mik ko biet

A=\(\frac{2}{1}\cdot3+\frac{2}{3}\cdot5+\frac{2}{5}\cdot7+\frac{2}{7}\cdot9\)

A=\(\frac{3}{1}\cdot2+\frac{5}{3}\cdot2+\frac{7}{5}\cdot2+\frac{9}{7}\cdot2\)

A=\(2\cdot\left(3+\frac{5}{3}+\frac{7}{5}+\frac{9}{7}\right)\)

A=\(2\cdot\frac{772}{105}\)

A=\(\frac{1544}{105}\)

A=\(14\frac{74}{105}\)

Giải đấy đủ giúp mình với 

a: =8/15x1/4=2/15

b: \(=\dfrac{5}{3}\cdot\dfrac{4}{5}\cdot\dfrac{6}{7}=\dfrac{24}{21}=\dfrac{8}{7}\)

c: \(=\dfrac{2}{5}\left(\dfrac{3}{7}+\dfrac{4}{7}\right)=\dfrac{2}{5}\)