`\text{1)}`
`\text{a)}`
`2/3 - 5/7 . 14/25`
`= 2/3 - {5 .1 4}/{7 . 25}`
`= 2/3 - 2/5`
`= 4/15`
`\text{b)}`
`3 1/3 + 0,75 - (-1/2)^3 + 2021^0`
`= 3 1/3 + 0,75 - {-1}/8 +1`
`= 3 1/3 + 0,75 + 1/8 +1`
`= 10/3 +3/4 + 1/8 + 1`
`= 10/3 + (3/4 + 1/8 + 8/8)`
`= 10/3 + (6/8 + 1/8 + 8/8)`
`=10/3 +15/8`
`= 125/24`
`\text{c)}`
`4/5 . 5/8+ 1/8 . 4/5 .4/5 . (-25%)`
`= 4/5( 5/8 + 1/8 + 1/4)`
`= 4/5( 5/8 + 1/8 + 2/8 )`
`= 4/5 . 1`
`= 4/5`
`\text{d)}`
`(-1/3)^2 + 60% +2 8/9 - 8/5`
`= 1/9 + 3/5 + 2 8/9 - 8/5`
`= (1/9 + 2 8/9) + (3/5 - 8/5)`
`=3 -1`
`= 2`
`\text{2)}`
`\text{a)}`
`1/9 : x = {-2}/45`
`-> x = 1/9 : {-2}/45`
`-> x = 1/9 . {-45}/2`
`-> x = {-5}/2`
Vậy `x = -5/2`
`\text{b)}`
`9/8 - 5/7x - 0,125 = 7/5`
`-> 9/8 - 5/7x = 7/5+0,125`
`-> 9/8 -5/7x = 61/40`
`-> 5/7x = {-2}/5`
`-> x = {-14}/25`
Vậy `x = {-14}/25`
`\text{c)}`
`2|x+ 2 5/6| = 14/13`
`-> |x + 17/6| = 7/13`
`->` \(\left[ \begin{array}{l}x+ \dfrac{17}{6}= \dfrac{7}{13}\\x+ \dfrac{17}{6}= \dfrac{-7}{13}\end{array} \right.\)
`->` \(\left[ \begin{array}{l}x= \dfrac{-179}{78} \\x= \dfrac{-263}{78}\end{array} \right.\)
Vậy `x \in { {-179}/78 ; {-263}/78 }`
`\text{d)}`
`5,5 - (1/2x +1/4) =1/2`
`-> 1/2x +1/4 = 5,5 - 0,5`
`-> 1/2x + 0,25 = 5`
`-> 0,5x = 4,75`
`-> x = 19/2`
Vậy `x = 19/2`
`\text{e)}`
`x -2/3x = 5/9x +6`
`-> x -2/3x - 5/9x = 6`
`->{-2}/9x = 6`
`-> x = -27`
Vậy `x = -27`
`\text{f)}`
`|x+1| +5 = 2|x+1|`
`5 = 2|x+1| - |x+1|`
`5 = |x+1|`
`->` \(\left[ \begin{array}{l}x+1 =5\\x+1=-5\end{array} \right.\)
`->` \(\left[ \begin{array}{l}x=4\\x= -6\end{array} \right.\)
Vậy `x \in {4 ;-6}`
