a: \(=\dfrac{7\cdot5+3\cdot9}{45}\cdot\dfrac{2}{3}=\dfrac{62}{45}\cdot\dfrac{2}{3}=\dfrac{124}{135}\)

b: \(=\dfrac{6}{11}\cdot\dfrac{5}{7}=\dfrac{30}{77}\)

c: \(=\dfrac{7}{8}\cdot\dfrac{8-3}{9}=\dfrac{7}{8}\cdot\dfrac{5}{9}=\dfrac{35}{72}\)

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\(\text{#TNam}\)

`a, (7/9+3/5) \times 2/3`

`C1:`

`=62/45 \times 2/3`

`= 124/135`

`C2:`

`= 7/9 \times 2/3 + 3/5 \times 2/3`

`= 14/27 +2/5`

`= 124/135`

`b, `

`C1:`

`= 6/11 \times 5/7`

`=`30/77`

`C2:

`= 9/11 \times 5/7-3/11 \times 5/7`

`= 45/77 -15/77`

`= 30/77`

`c,`

`C1:`

`= 7/8 \times 5/9`

`=35/72`

`C2:`

`= 7/8 \times 8/9- 7/8 \times 1/3`

`= 7/9-7/24`

`=35/72`

a.90

b.6

a, 90

b,6

a:=90

b:=6

a)2+4+8+6+7+8+3+9+2+1;

=(9+1)+(2+8)+(4+6)+(7+3)+(2+8)

=10+10+10+10+10

=10x5

=50

b)3+2+4+9+7+1+8+6+3+5

làm tương tự nhé

c)2+3+4+5+6+7+8+9+1+4.

làm tương tự nhé

P/s tham khảo nha

a) Bạn gộp các số có tổng bằng 10 :2-8,4-6,7-3,8-2,9-1 kq50

b)c) tương tự 

\

a)2+4+8+6+7+8+3+9+2+1

=(2+8)+(4+6)+(7+3)+(8+2)+(9+1)

=10+10+10+10+10

=50

b)3+2+4+9+7+1+8+6+3+5

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

=10+10+10+10+8

=48

c)2+3+4+5+6+7+8+9+1+4

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

=10+10+10+10+9

=49

b)

1 + 9 = 10     2 + 8 = 10     3 + 7 = 10     4 + 6 = 10

9 + 1 = 10     8 + 2 = 10     7 + 3 = 10     6 + 4 = 10

9 - 1 = 8     8 - 2 = 6     7 - 3 = 4     6 - 3 = 3

 a)\(\left(\dfrac{5}{6}+\dfrac{3}{8}\right)\times\dfrac{2}{7}\)

\(=\dfrac{29}{24}\times\dfrac{2}{7}\)

\(=\) \(\dfrac{29}{84}\)

b) \(\dfrac{6}{7}\times\dfrac{2}{3}\div\dfrac{5}{7}\)

= \(\dfrac{4}{7}\div\) \(\dfrac{5}{7}\)

= \(\dfrac{4}{5}\)

c) \(\dfrac{8}{9}+\dfrac{3}{4}\times\dfrac{4}{9}\)

= \(\dfrac{8}{9}+\dfrac{1}{3}\)

= \(\dfrac{5}{9}\)

Cô tích xanh cho lisa blackpink vì câu a, b đúng. Còn câu c thì em làm như sau:

c, \(\dfrac{8}{9}\) + \(\dfrac{3}{4}\) \(\times\) \(\dfrac{4}{9}\) 

  = \(\dfrac{8}{9}\) + \(\dfrac{1}{3}\)

  =  \(\dfrac{8}{9}\) + \(\dfrac{3}{9}\)

  =    \(\dfrac{11}{9}\)

a) 29/84

b) 4/5

c) 5/9

Là sao!!!!!???????!!!!!???

\(a.\dfrac{-3}{8}-\dfrac{13}{65}+\dfrac{3}{8}=\left(\dfrac{3}{8}-\dfrac{3}{8}\right)-\dfrac{13}{65}=-\dfrac{13}{65}\)

\(b.\left(\dfrac{-13}{7}-\dfrac{4}{9}\right)-\left(-\dfrac{10}{7}-\dfrac{4}{9}\right)=\dfrac{-13}{7}-\dfrac{4}{9}+\dfrac{10}{7}+\dfrac{4}{9}\\ =\left(\dfrac{-13}{7}+\dfrac{10}{7}\right)+\left(\dfrac{4}{9}-\dfrac{4}{9}\right)=-\dfrac{3}{7}\)

\(c.17\dfrac{1}{3}\cdot\left(\dfrac{-3}{7}\right)+3\dfrac{2}{3}\cdot\left(\dfrac{-3}{7}\right)=\dfrac{-3}{7}\cdot\left(17\dfrac{1}{3}+3\dfrac{2}{3}\right)\\ =\dfrac{-3}{7}\cdot\left(\dfrac{52}{3}+\dfrac{11}{3}\right)=\dfrac{-3}{7}\cdot21=-9\)

\(a,\left(-\dfrac{4}{9}\right)\times\dfrac{3}{8}+\dfrac{1}{18}=-\dfrac{1}{6}+\dfrac{1}{18}=\dfrac{-1.3}{6.3}+\dfrac{1}{18}=\dfrac{-3+1}{18}=-\dfrac{2}{18}=-\dfrac{1}{9}\)

xem lại đề câu b

\(c,\left(\dfrac{1}{2}-\dfrac{2}{3}\right)\times\dfrac{4}{4}=\dfrac{1}{2}-\dfrac{2}{3}=\dfrac{3-4}{6}=-\dfrac{1}{6}\\ d,\dfrac{9}{7}\times\left(\dfrac{3}{7}-\dfrac{1}{2}\right)=\dfrac{9}{7}\times\left(\dfrac{3.2-7}{14}\right)=\dfrac{9}{7}\times\dfrac{-1}{14}=-\dfrac{9}{98}\)