a) |x-5| = |-7|
|x-5| = 7
\( \Rightarrow \left[ {\begin{array}{*{20}{c}} {x - 5 = 7}\\ {x - 5 = - 7} \end{array}} \right. \Rightarrow \left[ {\begin{array}{*{20}{c}} {x = 7 + 5}\\ {x = \left( { - 7} \right) + 5} \end{array}} \right. \Rightarrow \left[ {\begin{array}{*{20}{c}} {x = 12}\\ {x = 2} \end{array}} \right.\)
Vậy x \(\in\) { 12;-2}
b) |x-3| = 7 - ( - 2 )
|x-3| = 7 + 2
|x-3| = 9\(\Rightarrow\left[{}\begin{matrix}x-3=9\\x-3=-9\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=9+3\\x=\left(-9\right)+3\end{matrix}\right.\Rightarrow}\left[{}\begin{matrix}x=12\\x=-6\end{matrix}\right.\)
Vậy x \(\in\) { 12 ; -6 }
c) ( 7 - x ) - ( 25 + 7 ) = - 25
( 7 - x ) - 32 = - 25
7 - x = ( - 25 ) + 32
7 - x = 7
x = 7 - 7
x = 0
