a)( \(\dfrac{-8}{40}\)+\(\dfrac{25}{40}\))+(\(\dfrac{-3}{8}\))

=\(\dfrac{17}{40}\)+(\(\dfrac{-3}{8}\))

=\(\dfrac{17}{40}\)+(\(\dfrac{-15}{40}\))

=\(\dfrac{2}{40}\)

=\(\dfrac{1}{20}\)

b)\(\dfrac{-5}{21}\)-(\(\dfrac{16}{21}\)-\(\dfrac{21}{21}\))

=\(\dfrac{-5}{21}\)-\(-5\)

=\(\dfrac{-25}{105}\)-\(\dfrac{-105}{105}\)

=\(\dfrac{16}{21}\)

bằng đây thôi nha mỏi tay quá

c: =3/7(-5/11+6/11)=3/7*1/11=3/77

d:=8/-3(4/3-7/3)=8/3

e: =3,4-5/8-0,4-3/8

=2-1

=1

21/32

2/9

7/10

1/15

21/32

2/9

7/10

1/15

\(\dfrac{7}{4}:\dfrac{8}{3}=\dfrac{21}{32}\)

\(\dfrac{7}{6}:\dfrac{21}{4}=\dfrac{28}{126}\)

\(\dfrac{8}{5}:\dfrac{16}{7}=\dfrac{56}{80}\)

\(\dfrac{5}{12}:\dfrac{25}{4}=\dfrac{20}{300}\)

Có gì you tự rút gọn nha :>

\(-\dfrac{7}{8}\times\dfrac{16}{21}-\dfrac{5}{3}\times\left(-\dfrac{1}{2}\right)=-\dfrac{2}{3}+\dfrac{5}{6}=-\dfrac{4}{6}+\dfrac{5}{6}=\dfrac{1}{6}\)

\(=\dfrac{-7}{8}\cdot\dfrac{16}{21}-\dfrac{5}{3}\cdot\dfrac{2-7}{10}=\dfrac{-2}{3}+\dfrac{5}{6}=\dfrac{1}{6}\)

\(\dfrac{1}{6}\)

\(\dfrac{1}{6}\)

7/4 : 8/3 = 7/4 x 3/8 = 21/32

7/6 : 21/4 = 7/6 x 4/21= 2/9

8/ 5 : 16/7 = 8/5 x 7/16 = 7/10

5/12 : 25/4 = 5/12 x 4/24 = 1/15

21/32

2/9 

7/10

1/15

21/32

2/9 

7/10

1/15

ai giúp mình với

\(\dfrac{-7}{8}:\dfrac{21}{16}-\dfrac{5}{3}.\left(\dfrac{1}{5}-\dfrac{7}{10}\right)\)

\(=\dfrac{-7}{8}.\dfrac{16}{21}-\dfrac{5}{3}.\left(\dfrac{-1}{2}\right)\)

\(=\dfrac{-2}{3}+\dfrac{5}{6}=\dfrac{1}{6}\)

\(=\dfrac{-7}{8}:\dfrac{21}{16}-\dfrac{5}{3}.\left(\dfrac{1}{5}-\dfrac{7}{10}\right)\\ =\dfrac{-7}{8}.\dfrac{16}{21}-\dfrac{5}{3}.\dfrac{-1}{2}\\ =\dfrac{2}{3}-\dfrac{-5}{6}=\dfrac{3}{2}\)

= 3/4 : 5/8 = 6/5

\(\dfrac{4}{7}\times\dfrac{21}{16}:\dfrac{5}{8}\)

\(=\dfrac{3}{4}:\dfrac{5}{8}=\dfrac{6}{5}\)

6/5

= 3/4 : 5/8 = 6/5

\(\dfrac{4}{7}\) x \(\dfrac{21}{16}:\dfrac{5}{8}\) \(=\dfrac{84}{112}:\dfrac{5}{8}\)

\(=\dfrac{3}{4}:\dfrac{5}{8}\)

\(=\dfrac{3}{4}\) x \(\dfrac{8}{5}\)

\(=\dfrac{24}{20}\)

\(=\dfrac{6}{5}\)

\(\dfrac{4}{7}\times\dfrac{21}{16}:\dfrac{5}{8}=\dfrac{3}{4}:\dfrac{5}{8}=\dfrac{3}{4}\times\dfrac{8}{5}=\dfrac{24}{45}=\dfrac{8}{15}\)

#Fox