`\text{1)}`

`\text{a)}`

`{-2}/3 . 15/4 - {-1}/5 : {1}/{-5}`

`= {-2 . 15}/{3.4} - 1`

`= {-1 . 5}/{1 . 2} -1`

`= {-5}/2 - 2/2`

`= {-7}/2`

`\text{b)}`

`{-3}/17 + 2/13 + {-31}/17 - 15/13`

`= ({-3}/7 + {-31}/17) + (2/13 - 15/13)`

`= {-34}/17 + {-13}/13`

`= -2 - 1`

`= -3` 

`\text{c)}`

`{-3}/5 . 1/{-9} + 7/{-18} . 3/{-5} + 3/{-5} . 5/6`

`= {-3}/5(1/{-9} + 7/{-18} + 5/6)`

`= {-3}/5 ( {-2}/18 + {-7}/18  + 15/18 )`

`= {-3}/5 . 1/3`

`= {-1}/5` 

`\text{d)}`

`(-25) + (-8) - (-23)`

`= -33 + 23`

`= -10`

`\text{e)}` 

`25% : ({-1}/3 + 5/6)`

`= 1/4 : ({-2}/6 +5/6)`

`= 1/4 : 1/2`

`= 1/4 . 2`

`= 1/2`

`\text{l)}`

`2/3 . 7/13 -2/3 . 3/13 - 1 8/39`

`= 2/3(7/13 - 3/13) - 1 8/39`

`= 2/3 . 4/13 - 1 8/39`

`= 8/39 - 1 8/39`

`= -1` 

`\text{2)}`

`\text{a)}`

`1/2x - 1/3 = -1 3/4`

`=> 1/2x - 1/3 = {-7}/4`

`=> 1/2x = {-7}/4 + 1/3`

`=> 1/2x = {-17}/12`

`=> x = {-17}/6`

Vậy `x = {-17}/6`

`\text{b)}`

`(2/5 +x) . {-3}/10 = -2 1/2`

`=> (2/5+x) . {-3}/10 = {-5}/2`

`=> 2/5+x = {25}/3`

`=> x = {119}/15`

Vậy `x = {119}/15`

`\text{c)}`

`{-2}/5x + 1/5 = 3/4`

`=> {-2}/5x = 11/20`

`=> x = {-11}/8`

Vậy `x = {-11}/8`

`\text{d)}`

`2|2x-1| - (-5)^2 = (-3)^0`

`=> 2|2x-1| - 25 = 1`

`=> 2|2x-1| = 26`

`=> |2x-1| = 13`

`=>`\(\left[ \begin{array}{l}2x - 1 = 13\\2x - 1 = -13\end{array} \right.\) 

`=>` \(\left[ \begin{array}{l}x= 7\\x = -6\end{array} \right.\) 

Vậy `x \in { 7 ; (-6)}`  

`\text{e)}`

`1/9 : x = {-2}/45`

`=> x = 1/9 : {-2}/45`

`=> x = 1/9 . {-45}/2`

`=> x = {-5}/2` 

Vậy `x = {-5}/2`

`\text{f)}`

`9/8 - 5/7x = 0,125`

`1,125 - 5/7x = 0,125`

`=> 5/7x = 1`

`=> x = 7/5` 

Vậy `x = 7/5`

`\text{g)}`

`|x+  2 5/6| = 11/24`

`=> |x +  17/6| = 11/24`

`=>` \(\left[ \begin{array}{l}x+ \dfrac{17}6 = \dfrac{11}{24}\\x+ \dfrac{17}6 = \dfrac{-11}{24}\end{array} \right.\) 

`=>`  \(\left[ \begin{array}{l}x=\dfrac{-19}{8}\\x=\dfrac{-79}{24}\end{array} \right.\) 

Vậy `x \in { {-19}/8 ; {-79}/24}`

`\text{h)}`

`3/4(x-1) + 1 3/5x - 30% = 2 4/15`

`=> 3/4x - 3/4 + 8/5x - 3/10 = 34/15`

`=> (3/4x +8/5x) + ({-3}/4 - 3/10) = 34/15`

`=> 47/20x - 21/20 = 34/15`

`=> 47/20x = 199/60`

`=> x = 199/141`

Vậy `x = 199/141`

Đáp án:

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