a) \(\dfrac{4}{24}+\dfrac{7}{6}=\dfrac{4}{24}+\dfrac{28}{24}=\dfrac{4+28}{24}=\dfrac{32}{24}=\dfrac{4}{3}\)

b) \(\dfrac{10}{15}-\dfrac{1}{3}=\dfrac{10}{15}-\dfrac{5}{15}=\dfrac{10-5}{15}=\dfrac{5}{15}=\dfrac{1}{3}\)

c) \(\dfrac{21}{28}-\dfrac{1}{4}=\dfrac{21}{28}-\dfrac{7}{28}=\dfrac{21-7}{28}=\dfrac{14}{28}=\dfrac{1}{2}\)

d) \(\dfrac{35}{40}+\dfrac{5}{8}=\dfrac{35}{40}+\dfrac{25}{40}=\dfrac{35+25}{40}=\dfrac{60}{40}=\dfrac{3}{2}\)

\(a)\dfrac{4}{24}=\dfrac{1}{6} \\ \dfrac{1}{6}+\dfrac{7}{6}\\ =\dfrac{8}{6}=\dfrac{4}{3}\\ b)\dfrac{10}{15}=\dfrac{2}{3}-\dfrac{1}{3}\\ =\dfrac{1}{3}\\ c)\dfrac{21}{28}=\dfrac{3}{4}\\ \dfrac{3}{4}-\dfrac{1}{4}\\ =\dfrac{2}{4}=\dfrac{1}{2}\\ d)\dfrac{35}{40}=\dfrac{7}{8}\\ \dfrac{7}{8}+\dfrac{5}{8}\\ =\dfrac{12}{8}=\dfrac{3}{2}\)

a) \(\dfrac{16}{24}-\dfrac{1}{3}=\dfrac{2}{3}-\dfrac{1}{3}=\dfrac{1}{3}\)

b ) \(\dfrac{4}{5}-\dfrac{12}{60}=\dfrac{4}{5}-\dfrac{1}{5}=\dfrac{4}{5}\)

c ) \(\dfrac{35}{50}-\dfrac{3}{10}=\dfrac{7}{10}-\dfrac{3}{10}=\dfrac{4}{10}=\dfrac{2}{5}\)

d ) \(\dfrac{21}{28}-\dfrac{1}{4}=\dfrac{3}{4}-\dfrac{1}{4}=\dfrac{2}{4}=\dfrac{1}{2}\)

\(\frac{9}{12}+\frac{4}{7}\)

\(=\frac{3}{4}+\frac{4}{7}\)

\(=\frac{37}{28}\)

\(\frac{5}{10}+\frac{21}{28}\)

\(=\frac{1}{2}+\frac{3}{4}\)

\(=\frac{5}{4}\)

\(\frac{7}{9}+\frac{15}{27}\)

\(=\frac{7}{9}+\frac{5}{9}\)

\(=\frac{12}{9}\)

9/12 + 4/7=37/28

5/10 + 21/28 = 5/4

7/9 + 15/27 = 4/3

Học sinh nhẩm và ghi kết quả như sau:

35 : 5 = 7

28 : 7 = 4

24 : 6 = 4

21 : 3 = 7

35 : 7 = 5

28 : 4 = 7

24 : 4 = 6

21 : 7 = 3

35 : 5 = 7

28 : 7 = 4

24 : 6 = 4

21 : 3 = 7

35 : 7 = 5

28 : 4 = 7

24 : 4 = 6

21 : 7 = 3

\(\frac{28}{35}\times\frac{15}{72}\times1\frac{7}{49}=\frac{4}{5}\times\frac{5}{24}\times\frac{8}{7}=\frac{160}{840}=\frac{4}{21}\)

Lời giải:
$\frac{20}{12}+\frac{36}{18}-\frac{21}{28}=\frac{5}{3}+2-\frac{3}{4}$

$=\frac{20}{12}+\frac{24}{12}-\frac{9}{12}=\frac{20+24-9}{12}=\frac{35}{12}$

\(=\dfrac{5}{3}+2-\dfrac{3}{4}=\dfrac{5.4+2.12-3.3}{12}=\dfrac{20+24-9}{12}=\dfrac{35}{12}\)

em oi bai ni anh chiu em a co chi em hoi ai nhe

A= 7 1 x 21 3 x 12 2 / 14 2 x 28 4 x 6 1

A= 1 x 3 x 2 / 2 x 4 x 1

A= 6/8

A= 3/4

A=7 1x21 3x12 2 /14 2x28 4x 6 1

A=1x3x2/2x4x1

A=6/8

A=3/4