\(\dfrac{x}{5}=\dfrac{26}{65}\)

\(\dfrac{x}{5}=\dfrac{2}{5}\)

\(x=2\)

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\(\dfrac{3}{x}=\dfrac{51}{85}\)

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

`x=5`

\(+,\dfrac{x}{5}=\dfrac{26}{65}\\ =>x=\dfrac{5\times26}{65}=2\\+, \dfrac{3}{x}=\dfrac{51}{85}\\ =>x=\dfrac{3\times85}{51}=5\)

\(a,\dfrac{x}{4}=\dfrac{15}{20}\\ \Rightarrow\dfrac{x}{4}=\dfrac{3}{4}\\ \Rightarrow x=3\\ b,\dfrac{15}{x}=\dfrac{25}{35}\\ \Rightarrow\dfrac{15}{x}=\dfrac{5}{7}\\ \Rightarrow\dfrac{15}{x}=\dfrac{15}{21}\\ \Rightarrow x=21\\ c,\dfrac{x}{5}=\dfrac{26}{65}\\ \Rightarrow\dfrac{x}{5}=\dfrac{2}{5}\\ \Rightarrow x=2\\ d,\dfrac{3}{x}=\dfrac{51}{85}\\ \Rightarrow\dfrac{3}{x}=\dfrac{3}{5}\\ \Rightarrow x=5\)

a,x4=1520⇒x4=34⇒x=3b,15x=2535⇒15x=57⇒15x=1521⇒x=21c,x5=2665⇒x5=25⇒x=2d,3x=5185⇒3x=35⇒x=5

51/85=39/65

15/21=25/35

\(\dfrac{51}{85}=\dfrac{39}{65}\)

\(\dfrac{15}{21}=\dfrac{25}{35}\)

26/39=38/57

55/77=25/35

39/65=51/85

kb với mình nha

Ban oi trình bay cả cách làm nữa nhé 

26/39 = 2/3

30/42=5/7

38/57=2/3

51/85=3/5

39/65=3/5

20/28=5/7

=> 39/65=51/85

=> 20/28=30/42

=> 26/39=38/57

k nhé

328185

507195

\(xxx+xx+x+x=992\)

\(111x+11x+x+x=992\)

\(x\times\left(111+11+1+1\right)=992\)

\(x\times124=992\)

\(x=992\div124\)

\(x=8\)

\(4725+xxx+xx+x=54909\)

\(4725+111x+11x+x=54909\)

\(4725+x\times\left(111+11+1\right)=54909\)

\(4725+x\times123=54909\)

\(x\times123=54909-4725\)

\(x\times123=20184\)

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