3(x-20%)- 7(5/14 - 3)=20
<=> 3x- 0,6- 35/14+ 21- 20=0
<=> 3x -21/10=0
<=> 3x= 21/10
<=> x= 7/10
Vậy x= 7/10
|2x +5|=1/3
<=> \(\left[ \begin{array}{l}2x+5= 1/3\\2x+ 5= -1/3\end{array} \right.\)
<=> \(\left[ \begin{array}{l}2x=-14/3\\2x=-16/3\end{array} \right.\)
<=> \(\left[ \begin{array}{l}x=-7/3\\x=-8/3\end{array} \right.\)
Vậy x ∈ { -7/3; -8/3}