@Mốc
a) $\frac{1}{2}$x + $\frac{3}{4}$ = $\frac{5}{6}$
<=> $\frac{1}{2}$x = $\frac{5}{6}$ - $\frac{3}{4}$
<=> $\frac{1}{2}$x = $\frac{10}{12}$ - $\frac{9}{12}$x
<=> $\frac{1}{2}$x = $\frac{1}{12}$x
<=> x = $\frac{1}{12}$ : $\frac{1}{2}$
<=> x = $\frac{1}{12}$ . 2
<=> x = $\frac{1}{6}$
b) 5 : x - 14 = $\frac{-7}{3}$
<=> 5 : x = $\frac{-7}{3}$ + 14
<=> 5 : x = $\frac{-7}{3}$ + $\frac{42}{3}$
<=> 5 : x = $\frac{35}{3}$
<=> x = 5 : $\frac{35}{3}$
<=> x = $\frac{3}{7}$
c) 7 : x + 2 = $\frac{3}{4}$
<=> 7 : x = $\frac{3}{4}$ - 2
<=> 7 : x = $\frac{3}{4}$ - $\frac{8}{4}$
<=> 7 : x = $\frac{-5}{4}$
<=> x = 7 : $\frac{-5}{4}$
<=> x = 7 . $\frac{4}{-5}$
<=> x = $\frac{-28}{5}$
d) | 5x - 3 | = 7
TH1: 5x - 3 = 7
<=> 5x = 7 + 3
<=> x = 10.
TH2: 5x - 3 = -7
<=> 5x = -4
<=> x = $\frac{-4}{5}$
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