`a) x-(-15)=3`
`→x+15=3`
`→x=3-15`
`→x=-12`
Vậy `x=-12`
`b)20-(x+12)=0`
`→x+12=20-0`
`→x+12=20`
`→x=20-12`
`→x=8`
Vậy `x=8`
`c)(5-x)-(-25+7) = -3+12`
`→5-x-(-18)=9`
`→5-x+18=9`
`→5-x=9-18`
`→5-x=-9`
`→x=5-(-9)`
`→x=14`
Vậy `x=14`
`d)|x+5|=2-(4-5)`
`→|x+5|=2-(-1)`
`→|x+5|=3`
`→` \(\left[ \begin{array}{l}x+5=3\\x+5=-3\end{array} \right.\)
`→` \(\left[ \begin{array}{l}x=-2\\x=-8\end{array} \right.\)
Vậy `x∈{-2;-8}`