3+2+2+2.8-1+4.1

=3+2+2+16-1+4

=(3+2+2-1)+(16+4)

=(5+2-1)+20

=(7-1)+20

=6+20

=26

1) Ta có: \(\left(\dfrac{3}{4}\cdot\dfrac{5}{97}+\dfrac{1}{9}\cdot\dfrac{13}{47}\right)\cdot\left(\dfrac{1}{5}-\dfrac{7}{25}\cdot\dfrac{5}{7}\right)\)

\(=\left(\dfrac{3}{4}\cdot\dfrac{5}{97}+\dfrac{1}{9}\cdot\dfrac{13}{47}\right)\cdot\left(\dfrac{1}{5}-\dfrac{1}{5}\right)\)

=0

2) Ta có: \(\dfrac{8}{17}\cdot\dfrac{4}{15}+\dfrac{8}{17}\cdot\dfrac{22}{15}-\dfrac{8}{15}\cdot\dfrac{9}{17}\)

\(=\dfrac{8}{17}\left(\dfrac{4}{15}+\dfrac{22}{15}-\dfrac{9}{15}\right)\)

\(=\dfrac{8}{17}\cdot\dfrac{15}{15}=\dfrac{8}{17}\)

3) Ta có: \(\dfrac{2021}{2}\cdot\dfrac{1}{3}+\dfrac{4042}{4}\cdot\dfrac{1}{5}+\dfrac{6063}{3}\cdot\dfrac{22}{15}\)

\(=\dfrac{2021}{2}\left(\dfrac{1}{3}+\dfrac{1}{5}\right)+2021\cdot\dfrac{22}{15}\)

\(=\dfrac{2021}{2}\cdot\dfrac{8}{15}+\dfrac{2021}{2}\cdot\dfrac{44}{15}\)

\(=\dfrac{2021}{2}\cdot\dfrac{52}{15}\)

\(=\dfrac{52546}{15}\)

4) Ta có: \(\dfrac{4}{7}\cdot\dfrac{2}{13}+\dfrac{8}{13}:\dfrac{7}{4}+\dfrac{4}{7}:\dfrac{13}{2}+\dfrac{4}{7}\cdot\dfrac{1}{13}\)

\(=\dfrac{4}{7}\left(\dfrac{2}{13}+\dfrac{8}{13}+\dfrac{2}{13}+\dfrac{1}{13}\right)\)

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

cảm ơn nhé

a) Cách 1 : (3/4 + 1/2) x 5/7

               = 5/4 x 5/7

                = 25/28

Cách 2 : (3/4 + 1/2) x 5/7

           = 3/4 x 5/7 + 1/2 x 5/7

            = 15/28 + 5/14

            = 25/28

b) Cách 1 : 5/7 x 13/21 + 2/7 x 13/21

= 65/147 + 26/147

= 13/21

Cách 2 : 5/7 x 13/21 + 2/7 x 13/21

= (5/7 + 2/7) x 13/21

= 1 x 13/21

= 13/21

câu c tự làm

8 /15 :2/3+7/15:2/3 =                                              tính bằng 2 cách nhé các bạn

a) \(\dfrac{1}{5}+\dfrac{4}{11}+\dfrac{1}{5}+\dfrac{7}{11}=\dfrac{1}{5}+\left(\dfrac{4}{11}+\dfrac{7}{11}\right)=\dfrac{1}{5}+1=\dfrac{1}{5}+\dfrac{5}{5}=\dfrac{6}{5}\)

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

22/7

7/5

43/4

15/28

1/42

7/12

1/4

2/5

5/12

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

a) X=3/18

b)X=13/10

c)X=11/15

d)X=8/35

e)X=37/21

f)X=65/36

g)X=1/4

h)X=5/4

i)X=7/5

k)X=5/14

l)X=167/96

có nhiều bài khó nếu em ko bik thì kb với cj để cj giúp nha.

a)3/8

b) 13/10

c) 11/15

d) 8/35

e) 37/21

f) 65/36

g) 1/4

h) 5/4

i) 7/5

k) 5/14

l) 167/96

-HT-  :)))))))