các phân số bằng nhau là : 

\(\frac{15}{25}=\frac{21}{35}=\frac{3}{5}=\frac{75}{125}\)

\(\frac{7}{4}=\frac{49}{28}=\frac{105}{60}\)

1.

a) \(\frac{16}{24}-\frac{1}{3}=\frac{16}{24}-\frac{8}{24}=\)\(\frac{8}{24}=\frac{1}{3}\)

b) \(\frac{4}{5}-\frac{12}{60}=\frac{48}{60}-\frac{12}{60}=\frac{36}{60}=\frac{9}{15}\)

3.

a)\(\frac{17}{6}-\frac{2}{6}=\frac{17-2}{6}=\frac{15}{6}\)

b) \(\frac{16}{15}-\frac{11}{15}=\frac{16-11}{15}=\frac{5}{15}=\frac{1}{3}\)

c) \(\frac{19}{12}-\frac{13}{12}=\frac{19-13}{12}=\frac{6}{12}=\frac{1}{2}\)

a) 16 24 − 1 3 = 16 24 − 8 24 = 24 16 ​ − 3 1 ​ = 24 16 ​ − 24 8 ​ = 8 24 = 1 3 24 8 ​ = 3 1 ​ b) 4 5 − 12 60 = 48 60 − 12 60 = 36 60 = 9 15 5 4 ​ − 60 12 ​ = 60 48 ​ − 60 12 ​ = 60 36 ​ = 15 9 ​ 3. a) 17 6 − 2 6 = 17 − 2 6 = 15 6 6 17 ​ − 6 2 ​ = 6 17−2 ​ = 6 15 ​ b) 16 15 − 11 15 = 16 − 11 15 = 5 15 = 1 3 15 16 ​ − 15 11 ​ = 15 16−11 ​ = 15 5 ​ = 3 1 ​ c) 19 12 − 13 12 = 19 − 13 12 = 6 12 = 1 2 12 19 ​ − 12 13 ​ = 12 19−13 ​ = 12 6 ​ = 2 1 ​

=> x/4 = 15/12 - 13/20

=> x/4 = 3/5

=> x = 3/5 x 4 

=> x = 12/5

Tk mk nha

\(\frac{2}{3}\) +    \(\frac{3}{4}\) =  \(\frac{8}{12}\) +   \(\frac{9}{12}\) = \(\frac{17}{12}\) 

\(\frac{5}{6}\) x   \(\frac{4}{15}\) =  \(\frac{2}{9}\)

\(\frac{4}{5}\) -   \(\frac{2}{7}\) = \(\frac{28}{35}\) -   \(\frac{10}{35}\) = \(\frac{18}{35}\) 

\(\frac{13}{9}\) :   \(\frac{5}{6}\) =  \(\frac{13}{9}\) x   \(\frac{6}{5}\) = \(\frac{26}{15}\) 

chúc bạn hok tốt ! 

\(\frac{2}{3}+\frac{3}{4}=\frac{8}{12}+\frac{9}{12}=\frac{17}{12}\)

\(\frac{5}{6}\) x \(\frac{4}{15}\) \(=\frac{5x6}{6x15}=\frac{1}{3}\)

\(\frac{4}{5}-\frac{2}{7}=\frac{28}{35}-\frac{10}{35}=\frac{18}{35}\)

\(\frac{13}{9}:\frac{5}{6}=\frac{13}{9}x\frac{6}{5}=\frac{13x6}{9x5}=\frac{26}{15}\)

Chúc bạn học tốt !

x/4 = 15/12 - 13/20

x/4 = 3/5

x = 3/5 . 4

x = 12/5

Vậy x=12/5

Tk mk nha

\(\frac{15}{12}-\frac{x}{4}=\frac{13}{20}\)

\(\frac{x}{4}=\frac{15}{12}-\frac{13}{20}\)

\(\frac{x}{4}=\frac{3}{5}\)

\(\Rightarrow x=2,4\)

\(a,\frac{10}{21}×\frac{14}{25}=\frac{4}{15}\)

\(b,3\frac{1}{3}×\frac{12}{35}=\frac{10}{3}×\frac{12}{35}=\frac{8}{7}\)

\(c,\frac{7}{15}×\frac{11}{13}+\frac{7}{15}×\frac{2}{13}+\frac{8}{15}=\frac{7}{15}+\frac{8}{15}=1\)

\(d,\left(\frac{41}{75}+\frac{17}{10}\right)×\frac{80}{129}=\frac{4}{9}\)

\(=\left(\frac{4}{17}+\frac{13}{17}\right)-\left(\frac{7}{15}+\frac{8}{15}\right)+\left(\frac{10}{16}-\frac{7}{16}\right)\)

\(=1-1+\frac{3}{16}\)

\(\frac{3}{16}\)

gộp 1,3 

2,4

5,6

thì ra 17/17-15/15+3/16=3/16

hk tốt!