\(=\left(\dfrac{9}{10}-\dfrac{7}{10}\right)+\left(\dfrac{7}{5}-\dfrac{6}{5}\right)=\dfrac{1}{5}+\dfrac{1}{5}=\dfrac{2}{5}\)

9/10+7/5-7/10-6/5

=( 9/10 - 7/10 ) + ( 7/5 - 6/5)

=1/5 + 1/5

=2/5

( 9/10 - 7/10 ) + ( 7/5 - 6/5 )

= 1/5 + 1/5

= 2/5

hummumumumhuhuhu=(

a: \(=\dfrac{4}{3}\cdot\dfrac{32}{10}+\dfrac{8}{3}\cdot\dfrac{36}{10}-\dfrac{4}{10}\cdot\dfrac{12}{9}\)

\(=\dfrac{128}{30}+\dfrac{288}{30}-\dfrac{48}{90}=\dfrac{416}{30}-\dfrac{24}{30}=\dfrac{392}{30}=\dfrac{196}{15}\)

\(\frac{13}{21}+3+\frac{29}{21}\)

\(=\frac{42}{21}+3\)

\(=2+3\)

\(=5\)

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

\(=\frac{3}{4}+\frac{3}{5}+\frac{1}{4}+\frac{2}{5}\)

\(=1+1\)

\(=2\)

a/(13/21 + 29/21) +3=42/21 +3 =2+3=5

b/ 3/4 + 3/5 +1/4 +2/5=(3/4+1/4)+(4/5+1/5)=1+1=2

lấy mt ra là xong

a) \(\dfrac{5}{9}+\dfrac{13}{7}+\dfrac{15}{13}+\dfrac{8}{7}+\dfrac{4}{9}+\dfrac{11}{13}\)

\(=\left(\dfrac{5}{9}+\dfrac{4}{9}\right)+\left(\dfrac{13}{7}+\dfrac{8}{7}\right)+\left(\dfrac{15}{13}+\dfrac{11}{13}\right)\)

\(=1+3+2\)

\(=6\)

b) \(\dfrac{3}{5}+\dfrac{18}{9}+\dfrac{4}{10}\)

\(=0,6+2+0,4\)

\(=\left(0,6+0,4\right)+2\)

\(=1+2\)

\(=3\)

\(a\dfrac{5}{9}+\dfrac{4}{9}+\dfrac{13}{7}+\dfrac{8}{7}+\dfrac{15}{13}+\dfrac{11}{13}=\dfrac{9}{9}+\dfrac{21}{7}+\dfrac{26}{13}=1+3+2=6\)

\(b\dfrac{3}{5}+2+\dfrac{2}{5}=\dfrac{5}{5}+2=1+2=3\)

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 : \(1+2+3+...+19+20\)

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

3x8/10+8/10x4+3x8/10

=8/10(3+4+3)

=8/10x 10

=8

=(1/11+10/11)+(2/11+9/11)+(3/11+8/11)+(4/11+7/11)+(5/11+6/11)

=11/11+11/11+11/11+11/11+11/11

=1+1+1+1+1

=5

=1+2+3+4+5+6+7+8+9+10 trên 11

= (1+9)+(2+8)+3+7)+(4+6)+5+10 trên 11

=10+10+10+10+10+5 trên 11

=10x5+5 trên 11

=50+5 trên 11

=55/11

=5

trên có nghĩa là (tất cả) phần 11 nha.

1/11+2/11+3/11+4/11+5/11+6/11+7/11+8/11+9/11+10/11

=(1/11+10/11)+(2/11+9/11)+(3/11+8/11)+(4/11+7/11)+(5/11+6/11)

=1+1+1+1+1

=5

chúc bạn học tốt!

= 11/11+ 15/15

= 1+ 1

= 2

= 11/11+ 15/15

= 1+ 1

= 2

tick cho mk

=(9/11+2/11)+(6/15+9/15)

=1+1

=2