Giải:
a) \(\left(-9\right)+10+\left(-10\right)+\left(-45\right)+55\)
\(=-9+10-10-45+55\)
\(=-9+\left(10-10\right)+\left(-45+55\right)\)
\(=-9+10=1\)
b) \(123+\left|-25\right|+\left(-\left|25\right|\right)-\left(-23\right)\)
\(=123+25+\left(-25\right)+23\)
\(=123+25-25+23\)
\(=123+\left(25-25\right)+23\)
\(=123+23=146\)