` 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

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

= 10 x 7/10

= 7

Chúc bạn học tốt!

= [ 3 + 5 + 2 ] x 7/10

= 10 x 7/10

= 70/10 = 7

(  3 + 5 + 2 ) x 7/10

10 x 7/10 = 70/10

= 7 Mik ko chắc nha.

.

\(\dfrac{7}{10}\left(4+3-7\right)=\dfrac{7}{10}\times0=0\)

\(\dfrac{7}{10}\left(4+3-7\right)=\dfrac{7}{10}\times0=0\)

= 7/10 x(4 + 3 - 7)

= 0

\(3\times\dfrac{7}{10}+\dfrac{7}{10}\times5+2\times\dfrac{7}{10}\)

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

\(=\dfrac{7}{10}\times10=7\)

7

=7/10×(3+5+2)=7/10×(3+5+2)

1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20

=(1+19)+(2+18)+(3+17)+(4+16)+(5+15)+(6+14)+(7+13)+(8+12)+(9+11)+20+10

=20+20+20+20+20+20+20+20+20+20+10

=20×10+10

=200+10

=210

= ( 1 + 19 ) + ( 2 + 18 ) + ( 3 + 17 ) + (4 + 16 ) + ( 5 + 15 ) + ( 6 + 14 ) + ( 7 + 13 ) + ( 8 + 12) + ( 9+ 11 ) + 20

= 20 + 20 + 20 +20 +  20 +20 + 20 + 20 + 20 +20

= 20 x 10

= 200

tui đầu tiên đó 

Ta có : \(1+2+3+...+19+20\)

          \(=\frac{\left(20+1\right).20}{2}=\frac{21.20}{2}=210\)

\(\frac{9}{10}+\frac{7}{9}+\frac{5}{8}+\frac{3}{7}+\frac{3}{5}+\frac{2}{5}+\frac{4}{7}+\frac{3}{8}+\frac{2}{9}+\frac{1}{10}\)\(\frac{1}{10}\)

= ( 9/10 + 1/10 ) + ( 7/9 + 2/9 ) + ( 5/8 + 3/8 ) + ( 3/7 + 4/7 ) + ( 3/5 + 2/5 )

= 1 + 1 + 1 + 1 + 1

=   1 x 5

=     5

\(\left(\frac{9}{10}+\frac{1}{10}\right)+\left(\frac{7}{9}+\frac{2}{9}\right)+\left(\frac{5}{8}+\frac{3}{8}\right)+\left(\frac{3}{7}+\frac{4}{7}\right)+\left(\frac{3}{5}+\frac{2}{5}\right)\)2/5)

=1+1+1+1+1=5

.

( 9/ 10 + 1/10 ) + ( 7/9 + 2/9) + ( 5/8 + 3/8 ) + ( 3/7 + 4/ 7) + ( 2/5 + 3/5 ) = 1 + 1+ 1+1 + 1 = 5