19/20x2/100+19/20x2/100

= [19/20+19/20]x2/100

= 38/20x2/100

= 19/500

75/76x102/100-75/76x2/100

= [102/100-2/100]x75/76

= 1x75/76

= 75/76

3x7/10+7/10x5+2x7/10

= [3+5+2]x7/10

= 10x7/10

= 7

giá trị biểu thức 

2/5+2/3x3/4

= 2/5+1/6

= 17/30

1/2x1/3-1/8

= 1/6-1/8

= 1/24

[1/2+1/3]:3/9

= 5/6:3/9

= 5/2

                       nhớ tick cho tớ nhé

rùi đó

cứu

`3 xx 7/10 + 7/10 xx 5 + 2 xx 14/20`

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

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

`= 10 xx 7/10`

`= 70/10`

`=7`

` 3xx 7/10 + 7/10 xx 5 +2 xx 7/10`

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

`= 7/10 xx 10`

`=7`

\(3\times\dfrac{7}{10}+\dfrac{7}{10}\times5+2\times\dfrac{7}{10}=\dfrac{7}{10}\times\left(3+5+2\right)=\dfrac{7}{10}\times10=7\)

7

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

=7/10 x 10

= 7

3x7/10+7/10x5+2x7/10

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

=7/10x10

=7

(Dấu . là dấu nhân nha e, tại e mới học lớp 4 nên chưa biết)

\(3.\frac{7}{10}+\frac{7}{10}.5+2.\frac{7}{10}=\frac{7}{10}.\left(3+5+2\right)=\frac{7}{10}.10=7\)

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

Đáp án của mình là: 7

b,8/3-x=9/10x5/3=3/2

=>x=8/3-3/2=7/6

c,x:5/9=2-11/8=5/8

=>x=5/8x5/9=25/72

d,x\(\cdot\)2/3+x\(\cdot\)7/3=11/4

=>x(2/3+7/3)=11/4

=>x=11/4:(2/3+7/3)=11/4:10/3=33/40.

\(b,\dfrac{8}{3}-x=\dfrac{9}{10}\times\dfrac{5}{3}\\ \Leftrightarrow x=\dfrac{7}{6}\)

\(c,x:\dfrac{5}{9}=2-\dfrac{11}{8}\\ \Leftrightarrow x=\dfrac{25}{72}\)

\(d,x\times\dfrac{2}{3}+x\times\dfrac{7}{3}=\dfrac{11}{4}\\ \Leftrightarrow3x=\dfrac{11}{4}\\ \Leftrightarrow x=\dfrac{11}{12}\)

 ko biết haha

a: \(=\dfrac{2^{10}\cdot3^8-2^{10}\cdot3^9}{2^{10}\cdot3^8+2^{10}\cdot3^8\cdot5}=\dfrac{2^{10}\cdot3^8\left(1-3\right)}{2^{10}\cdot3^8\left(1+5\right)}=\dfrac{-2}{6}=\dfrac{-1}{3}\)

b: \(=\dfrac{5^{16}\cdot3^{21}}{5^{15}\cdot3^{22}}=\dfrac{5}{3}\)

a) \(\dfrac{2}{5}-\dfrac{3}{15}\)

\(=\dfrac{2}{5}-\dfrac{3:3}{15:3}\)

\(=\dfrac{2}{5}-\dfrac{1}{5}\)

\(=\dfrac{1}{5}\)

b) \(\dfrac{9}{27}-\dfrac{2}{9}\)

\(=\dfrac{9:3}{27:3}-\dfrac{2}{9}\)

\(=\dfrac{3}{9}-\dfrac{2}{9}\)

\(=\dfrac{1}{9}\)

c) \(\dfrac{18}{24}-\dfrac{4}{8}\)

\(=\dfrac{18:6}{24:6}-\dfrac{4:2}{8:2}\)

\(=\dfrac{3}{4}-\dfrac{2}{4}\)

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

d) \(\dfrac{6}{16}-\dfrac{10}{64}\)

\(=\dfrac{6\times2}{16\times2}-\dfrac{10:2}{64:2}\)

\(=\dfrac{12}{32}-\dfrac{5}{32}\)

\(=\dfrac{7}{32}\)