a; \(\dfrac{3}{5}\) - \(\dfrac{-7}{10}\) - \(\dfrac{13}{-20}\)

= \(\dfrac{12}{20}\) +  \(\dfrac{14}{20}\) + \(\dfrac{13}{20}\)

= \(\dfrac{39}{20}\)

b; \(\dfrac{1}{2}\) + \(\dfrac{1}{-3}\) + \(\dfrac{1}{4}\) - \(\dfrac{-1}{6}\)

= \(\dfrac{6}{12}\) - \(\dfrac{4}{12}\) + \(\dfrac{3}{12}\) + \(\dfrac{2}{12}\)

= \(\dfrac{7}{12}\)

\(\left(\frac{3}{10}+\frac{4}{5}\cdot\frac{1}{2}\right):\left(\frac{18}{9}-\frac{1}{\frac{1}{3}}\right)\)

\(=\frac{7}{10}:\left(-1\right)=\frac{-7}{10}\)

(3/10+4/5*1/2):(18/9-1/1/3)

=(3/10+4/10):(2-1/3)

=7/10:5/3=1/10.3/5

=21/50
lưu ý: 1/1/3=1:1:3=1/3 nha bn

\(\left(\frac{3}{10}+\frac{4}{5}\cdot\frac{1}{2}\right):\left(\frac{18}{9}-\frac{1}{\frac{1}{3}}\right)\)

\(=\left(\frac{3}{10}+\frac{4}{10}\right):\left(2-1:\frac{1}{3}\right)\)

\(=\frac{7}{10}:\left(2-3\right)\)

\(=\frac{7}{10}:\left(-1\right)=-\frac{7}{10}\)

a; -\(\dfrac{4}{9}.\dfrac{7}{15}+\dfrac{4}{-9}.\dfrac{8}{15}\)

= - \(\dfrac{4}{9}\).(\(\dfrac{7}{15}+\dfrac{8}{15}\))

= - \(\dfrac{4}{9}\).1

= - \(\dfrac{4}{9}\)

b; - \(\dfrac{5}{4}.\dfrac{16}{25}\) + \(\dfrac{-5}{4}\).\(\dfrac{9}{25}\)

= - \(\dfrac{5}{4}\).(\(\dfrac{16}{25}\) + \(\dfrac{9}{25}\))

= - \(\dfrac{5}{4}\). 1

= - \(\dfrac{5}{4}\)

c; \(-\dfrac{5}{12}.\dfrac{4}{19}\) + \(\dfrac{-7}{12}.\dfrac{4}{19}-\dfrac{40}{57}\)

= - \(\dfrac{5}{12}\).\(\dfrac{4}{19}\) - \(\dfrac{7}{12}\).\(\dfrac{4}{19}\) - \(\dfrac{4}{19}\).\(\dfrac{10}{3}\)

= - \(\dfrac{4}{19}\).(\(\dfrac{5}{12}\) + \(\dfrac{7}{12}\) + \(\dfrac{10}{3}\))

= - \(\dfrac{4}{19}\).\(\dfrac{13}{3}\)

= - \(\dfrac{52}{57}\)

Chọn C

- Quãng đường sửa được trong ngày đầu là : \(\dfrac{9}{10}\left(km\right)\)

- Quãng đường sửa được trong ngày đầu là : \(\dfrac{9}{10}+\dfrac{1}{4}\left(km\right)\)

- Quãng đường sửa được trong ngày đầu là : \(\dfrac{9}{10}-\dfrac{1}{5}\left(km\right)\)

Vậy quãng đường đội công nhân sửa trong ba ngày là :

\(S=\dfrac{9}{10}+\dfrac{9}{10}+\dfrac{1}{4}+\dfrac{9}{10}-\dfrac{1}{5}=\dfrac{11}{4}\left(km\right)\)

cái cuối chưa có dấu = nha sorry

\(\frac{7}{8}-\frac{1}{3}=\frac{21}{24}-\frac{8}{24}=\frac{13}{24}\)

\(\frac{8}{9}+\frac{2}{5}=\frac{40}{45}+\frac{18}{45}=\frac{58}{45}\)

\(\frac{3}{10}\times\frac{1}{6}=\frac{3\times1}{10\times6}=\frac{3}{60}=\frac{1}{20}\)

\(\frac{8}{9}:\frac{3}{7}=\frac{8}{9}\times\frac{7}{3}=\frac{8\times7}{9\times3}=\frac{56}{27}\)

7/8 - 1/3 = 13/24

8/9 + 2/5 = 58/45

3/10 x 1/6 = 3/60

8/9 : 3/7 = 56/27

#vanh#

Bài 1:

Giờ đầu bán được số quả dưa là:

     44.\(\frac{1}{3}\)+\(\frac{1}{3}\) = 15 (quả)

Giờ thứ hai bán được số quả dưa là:

     (44-15).\(\frac{1}{3}\)+ \(\frac{1}{3}\)= 10 (quả)

Giờ thứ ba bán được số quả là: 

     44-15-10 = 19 (quả) 

                      Đáp số: 19 quả

*Bài 2 mình hông có biết làm. Thứ lỗi nha

\(\left(\dfrac{3}{10}+\dfrac{4}{5}\cdot\dfrac{1}{2}\right):\left(\dfrac{18}{9}-1\dfrac{1}{3}\right)\)

\(=\left(\dfrac{3}{10}+\dfrac{4}{10}\right):\left(\dfrac{6}{3}-\dfrac{4}{3}\right)\)

\(=\dfrac{7}{10}:\dfrac{2}{3}=\dfrac{7}{10}\cdot\dfrac{3}{2}=\dfrac{21}{20}\)

a; 0,2.\(\dfrac{15}{36}\) - (\(\dfrac{2}{5}\) + \(\dfrac{2}{3}\)): 1%

   = \(\dfrac{1}{12}\)  - \(\dfrac{16}{15}\): \(\dfrac{1}{100}\)

  =    \(\dfrac{1}{12}\) - \(\dfrac{320}{3}\)

= \(\dfrac{1}{12}\) - \(\dfrac{1280}{12}\)
= - \(\dfrac{1279}{12}\)

b; 75% - 1\(\dfrac{1}{2}\) + 0,5 : \(\dfrac{5}{12}\)

= 0,75 - 1,5 + 1,2

= -0,75 + 1,2

= 0,45

c; 1\(\dfrac{3}{15}.0,75-\left(\dfrac{8}{15}+0,25\right)\).\(\dfrac{24}{47}\)

= \(\dfrac{28}{15}\).0,75 - \(\dfrac{47}{60}\).\(\dfrac{24}{47}\)

= \(\dfrac{7}{5}-\dfrac{2}{5}\)

= 1

d; \(\dfrac{32}{15}\): (-1\(\dfrac{1}{5}\) + 1\(\dfrac{1}{3}\))

= \(\dfrac{32}{15}\): (-\(\dfrac{6}{5}\) + \(\dfrac{4}{3}\))

= \(\dfrac{32}{15}\): \(\dfrac{2}{15}\)

= 16

e; 20 + 9\(\dfrac{1}{4}:2\dfrac{1}{4}\)

= 20 + \(\dfrac{37}{4}\) : \(\dfrac{9}{4}\)

= 20 + \(\dfrac{37}{9}\)

= \(\dfrac{217}{9}\)

g; \(\dfrac{3}{4}.\dfrac{16}{9}\)- \(\dfrac{7}{5}\): (-\(\dfrac{21}{20}\))

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

= \(\dfrac{4}{3}\) + \(\dfrac{4}{3}\)

= \(\dfrac{8}{3}\)

\(\frac{3}{5}=\frac{6}{10}=\frac{9}{15}=\frac{12}{20}\)

\(\frac{3}{5}=\frac{6}{10}=\frac{9}{15}=\frac{12}{20}\)

\(\frac{3}{5}=\frac{?}{10}=\frac{9}{?}=\frac{?}{20}\)

Ta có:

\(\frac{3}{5}=\frac{?}{5x2}=\frac{3x2}{?}=\frac{?}{5x4}\)

\(\frac{3}{5}=\frac{3x2}{5x2}=\frac{3x2}{5x2}=\frac{3x4}{5x4}\)

\(\frac{3}{5}=\frac{9}{10}=\frac{9}{10}=\frac{12}{20}\)

Chỗ đây bn tự điền ? nha