Bài $1$.
$a$) `1/5 + 5/7 : 15/14 - 1,5`
`= 1/5 + 5/7 . 14/15 - 1,5`
`= 1/5 + 2/3 - 3/2`
`= -19/30`
$b$) `7 11/6 - (3 5/9 - 2 7/6) + 6 5/9`
`= 53/6 - 32/9 + 19/6 + 59/9`
`= {72}/6 +{27}/9`
`= 12 + 3`
`= 15`
$c$) `(-3/2)^2 - | -2/15| . 25/4 + 35\%`
`= 9/4 - 2/15 . 25/4 + 7/20`
`= 9/4 - 5/6+ 7/20`
`= 53/30`
$d$) `(-1/2)^2 : 3/4 - 50\% . (-2 1/2) - |-0,45|`
`= 1/4 . 4/3 - 1/2 . {-5}/2 - 0,45`
`= 1/3 - {-5}/4 - 0,45`
`= 17/15`
Bài $2$.
$a$) `x-2,5 = 3 3/10`
`⇔ x - 5/2 = 33/10`
`⇔ x = 29/5`
Vậy `x=29/5`
$b$) `3 1/4 . x - 2/5 = 1/4 . x + 3/10`
`⇔ 13/4x - 1/4 x = 3/10 + 2/5`
`⇔ 3x = 7/10`
`⇔ x = 7/30`
Vậy `x=7/30`
$c$) `-27/{x+5} = {x+5}/-3`
`⇔ (x+5)^2 = 81`
`⇔ x+5 = ±9`
`⇒` \(\left[ \begin{array}{l}x=4\\x=-14\end{array} \right.\)
Vậy $x$ $∈$ `{4;-14}`
$d$) `1 - 3|2x - 1/3| = 25\%`
`⇔3|2x-1/3| = 3/4`
`⇔ |2x-1/3| = 1/4`
`⇒` \(\left[ \begin{array}{l}x=\dfrac{7}{24}\\x=\dfrac{1}{24}\end{array} \right.\)
Vậy $x$ $∈$ `{7/24;1/24}`
