`\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`
