`x/7 = 22/77`

`=>77x= 22.7`

`=>77x= 154`

`=>x=154:77`

`=>x=2`

\(\dfrac{2}{7}\)= \(\dfrac{22}{77}\)

2 nha

\(\dfrac{1}{3}< \dfrac{1}{2}< \dfrac{2}{3}\)

$\frac{1}{3}$< $\frac{x}{2}$< $\frac{2}{3}$

$\Rightarrow$$\frac{2}{6}$< $\frac{x\times 3}{6}$< $\frac{4}{6}$

$\Rightarrow$ 2 < x $\times$3 < 4

$\Rightarrow$x $\times$3 = 3

x = 3 $÷$3

x = 1

\(\dfrac{1}{3}< \dfrac{x}{2}< \dfrac{2}{3}\)

->  \(\dfrac{2}{6}< \dfrac{2x}{6}< \dfrac{4}{6}\)

-> \(2< 2x< 4\)

-> \(1< x< 2\) 

Vậy x nằm trong khoảng 1 < x < 2

=>80<11x<100

=>11x=88 hoặc 11x=99

=>x=8 hoặc x=9

`4/11<x/20<5/11`

`=>80/220<11x/220<100/220`

`=>80<11x<100`

`=> x=8` hoặc `x=9`

=>67-x=28

hay x=39

=>67-x = 7/19 x 76

67-x=28

x=67-28

x=39

\(19(67-x)=532=>1273-19x=532=>19x=67=>x=39\)

\(\dfrac{1}{x}+\dfrac{y}{3}=\dfrac{5}{6}\Rightarrow\dfrac{6}{6x}+\dfrac{2xy}{6x}=\dfrac{5x}{6x}\Rightarrow6+2xy=5x\)

\(\Rightarrow5x-2xy=6\Rightarrow x\left(5-2y\right)=6\)

Do \(x,y\) là số tự nhiên nên \(x\inƯ^+\left(6\right)\)

TH1: \(x=1\Rightarrow5-2y=6\Rightarrow y=-\dfrac{1}{2}\) (loại)

TH2: \(x=2\Rightarrow5-2y=3\Rightarrow y=1\) (TM)

TH3: \(x=3\Rightarrow5-2y=2\Rightarrow y=\dfrac{3}{2}\) (Loại)

TH4: \(x=6\Rightarrow5-2y=1\Rightarrow y=2\) (TM)

\(\Leftrightarrow6+2xy=5x\left(x\ne0\right)\)

\(\Leftrightarrow5x-2xy=6\Leftrightarrow x\left(5-2y\right)=6\)

\(\Leftrightarrow x=\dfrac{6}{5-2y}\) 

Để x nguyên thì 5-2y phải là ước của 6

\(\Rightarrow5-2y=\left\{-6;-3;-2;-1;1;2;3;6\right\}\)

\(\Rightarrow y=\left\{4;3;2;1\right\}\Rightarrow x=\left\{-2;-6;6;2\right\}\)

x=2

y=1

1.

=2/5 x 12/3 + 2/5 x 15/3 + 2/5 x 1

= 2/5 x (12/3 + 15/3 + 1)

=2/5 x 1

=2/5

2.a=1;2

Bài 1: Ta có: \(4\dfrac{3}{5}+\dfrac{7}{10}< X< \dfrac{20}{3}\)

\(\dfrac{23}{5}+\dfrac{7}{10}< X< \dfrac{20}{3}\)

\(\dfrac{138}{30}< X< \dfrac{200}{3}\)

\(\Rightarrow X\in\left\{\dfrac{160}{30};\dfrac{161}{30};\dfrac{162}{30};...;\dfrac{198}{30};\dfrac{199}{30}\right\}\)

Bài 2: \(X-2019\dfrac{2}{13}=3\dfrac{7}{26}+4\dfrac{7}{52}\)

\(\Rightarrow X-\dfrac{26249}{13}=\dfrac{85}{26}+\dfrac{215}{52}\)

\(\Rightarrow X-\dfrac{26249}{13}=\dfrac{385}{52}\)

\(\Rightarrow X=\dfrac{105381}{52}\)

=> 1/x = 5/6 - y/3

1/x = 5-2y/6

=> x(5-2y) = 1.6 = 6

Do x ∈ N => x >= 0

Mà 6>0 => 5-2y > 0

Vì y ∈ N => 5-2y ∈ N*

Ta có bảng:

Do x,y ∈ N => (x,y) = (6,2) (thử lại thỏa mãn)

Vậy x=6; y = 2

a: \(\Leftrightarrow\left[{}\begin{matrix}x=3\\x=-1\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}B=\dfrac{-3}{3-1}=\dfrac{-3}{2}\\B=\dfrac{-\left(-1\right)}{3-\left(-1\right)}=\dfrac{1}{4}\end{matrix}\right.\)