`a, x - 5/6 = 4/5`
$\Rightarrow$ `x = 4/5 + 5/6`
$\Rightarrow$ `x = 49/30`
$\text{Vậy}$ `x = 49/30`
_____________
`b, \sqrt{x - 3} = 2` `(x \ge 3)`
$\Rightarrow$ `x - 3 = 2^{2}`
$\Rightarrow$ `x - 3 = 4`
$\Rightarrow$ `x = 4 + 3`
$\Rightarrow$ `x = 7`
$\text{Vậy}$ `x = 7`
_______________
`c, |x - 3/4| - 0,5 = 0`
$\Rightarrow$ `|x - 3/4| = 0 + 0,5`
$\Rightarrow$ `|x - 3/4| = 0,5`
$\Rightarrow$ `|x - 3/4| = 1/2`
$\text{TH1:}$
`x - 3/4 = 1/2`
$\Rightarrow$ `x = 1/2 + 3/4`
$\Rightarrow$ `x = 5/4`
$\text{TH2:}$
`x - 3/4 = -1/2`
$\Rightarrow$ `x = -1/2 + 3/4`
$\Rightarrow$ `x = 1/4`
$\text{Vậy}$ `x \in {5/4 ; 1/4}`
