51/30

24/65

chưa xong 

\(\frac{12}{1}:\frac{6}{5}+\frac{4}{7}=\frac{60}{6}+\frac{7}{4}=\frac{10}{1}+\frac{7}{4}=\frac{40}{4}+\frac{7}{4}=\frac{47}{4}\)

\(\left(\frac{5}{6}+\frac{3}{4}\right)\cdot\frac{8}{19}=\frac{38}{24}\cdot\frac{18}{9}=\frac{38}{24}\cdot2=\frac{76}{24}=\frac{19}{6}\)

\(\left(\frac{7}{4}-\frac{5}{3}\right)\cdot\frac{2}{3}=\frac{1}{12}\cdot\frac{2}{3}=\frac{1}{13}\)

câu 1 : 62/35

câu 2 : 2/3

câu 3 : 1/18

nhớ tk m nhé

câu 1: 12:6/5+4/7=47/21

câu 2: (5/6+3/4):19/8=2/3

câu 3: (7/4-5/3):3/2=1/18

Chọn đáp án: B. Các câu 1 – 2 – 4 – 6 – 8

Chọn C

khỏi chép đề nha

a\Câu 1:

200 : ( 15 - x ) = 15 + 5

200 : ( 15 - x ) = 20

15 - x = 200 : 20

15 - x = 10

x = 15 - 10

x = 5

Câu 2:

63 : ( x - 5 ) = 22 -1

63 : ( x - 5 ) = 21

x - 5 = 63 : 21

x - 5 = 3

x = 3 + 5

x = 8

\(\frac{1}{3}:x-\frac{2}{3}=\frac{5}{6}+\frac{7}{8}\)

\(\frac{1}{3}:x-\frac{2}{3}=\frac{41}{24}\)

\(\frac{1}{3}:x=\frac{19}{8}\)

\(x=\frac{8}{57}\)

\(\frac{2}{5}-x:\frac{3}{5}=\frac{6}{7}\)

\(x:\frac{3}{5}=\frac{-16}{35}\)

\(x=\frac{-48}{175}\)

\(\frac{4}{5}-\frac{26}{m}=\frac{-8}{15}\)

\(\frac{26}{m}=\frac{4}{3}\)

=> 26 x 3 = m x 4

   78 = m x 4

         m = 19,5

Câu 1 :\(\frac{1}{3}\div x-\frac{2}{3}=\frac{5}{6}+\frac{7}{8}\)

\(\Leftrightarrow\frac{1}{3x}=\frac{5}{6}+\frac{7}{8}+\frac{2}{3}\)

\(\Leftrightarrow\frac{1}{3x}=\frac{4\cdot5}{24}+\frac{7\cdot3}{24}+\frac{2\cdot8}{24}\)

\(\Leftrightarrow\frac{1}{3x}=\frac{20}{24}+\frac{21}{24}+\frac{16}{24}\)

\(\Leftrightarrow\frac{1}{3x}=\frac{57}{24}\)

\(\Leftrightarrow24=57\cdot3x\)

\(\Leftrightarrow24=171x\)

\(\Leftrightarrow x=\frac{24}{171}=\frac{8}{57}\)

Câu 2: \(\frac{2}{5}-x\div\frac{3}{5}=\frac{6}{7}\)

\(\Leftrightarrow\frac{-5x}{3}=\frac{6}{7}-\frac{2}{5}\)

\(\Leftrightarrow\frac{-5x}{3}=\frac{5\cdot6}{35}-\frac{2\cdot7}{35}\)

\(\Leftrightarrow\frac{-5x}{3}=\frac{30}{35}-\frac{14}{35}\)

\(\Leftrightarrow-\frac{5x}{3}=\frac{16}{35}\)

\(\Leftrightarrow-175x=48\)

\(\Leftrightarrow x=-\frac{48}{175}\)

Câu 3: \(\frac{4}{5}-\frac{26}{m}=-\frac{8}{15}\)

\(\Leftrightarrow\frac{26}{m}=\frac{4}{5}-\left(-\frac{8}{15}\right)\)

\(\Leftrightarrow\frac{26}{m}=\frac{4}{5}+\frac{8}{15}\)

\(\Leftrightarrow\frac{26}{m}=\frac{12}{15}+\frac{8}{15}\)

\(\Leftrightarrow\frac{26}{m}=\frac{20}{15}\)

\(\Leftrightarrow20m=26\cdot15=390\)

\(\Leftrightarrow m=\frac{390}{20}=\frac{39}{2}\)

1. a

\(\dfrac{8}{5}-\dfrac{5}{6}\cdot\dfrac{3}{4}\)

\(=\dfrac{8}{5}-\dfrac{5\cdot3}{3\cdot2\cdot4}\)

\(=\dfrac{8}{5}-\dfrac{5}{8}=\dfrac{39}{40}\)

1.b

\(=\dfrac{7}{8}+\dfrac{5}{6}\cdot\dfrac{3}{2}\)

\(=\dfrac{7}{8}+\dfrac{5\cdot3}{3\cdot2\cdot2}\)

\(=\dfrac{7}{8}+\dfrac{5}{4}=\dfrac{17}{8}\)

2.a

\(\dfrac{4}{5}+x=\dfrac{11}{10}\)

\(x=\dfrac{11}{10}-\dfrac{4}{5}=\dfrac{3}{10}\)

2.b

\(x-\dfrac{3}{4}=\dfrac{5}{7}\)

\(x=\dfrac{5}{7}+\dfrac{3}{4}=\dfrac{41}{28}\)

a, 13/6+5/8 : -3/4 - 7/12.4

= 13/6 + -5/6-7/3

=8/6-7/3

= -6/6

= -1

b, ( 73/5 - 21/3) + ( 4/3-43/5 )

= 73/5-21/3+4/3-43/5

=( 73/5-43/5)-(21/3-4/3)

= 6-17/3

=1/3

c, 7/5.4/9 +7/5: 9/16- 14/10.2/9

= 7/5.4/9 +7/5.16/9 - 14/45

=7/5.(4/9+16/9)-14/45

=7/5.20/9-14/45

= 140/45 - 14/45

= 126/45

Xong rùi nè! Nhưng bạn kiểm tra lại giùm nhé vì làm vào ban đêm nên hơi bất tiện

Trời ạ. 7 3/5 chứ k phải 73/5 -_-

ghi rõ thêm từ và nhé!

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