a: \(\left(45+24\right)+\left(231-45-24\right)\)
\(=45+24+231-45-24\)
\(=231+\left(45-45\right)+\left(24-24\right)\)
\(=231+0+0=231\)
b: \(\left(32-78+12\right)-\left(32+12\right)\)
\(=32-78+12-32-12\)
\(=-78+\left(32-32\right)+\left(12-12\right)\)
\(=-78+0+0=-78\)
c: \(\left(243+597\right)+\left(1996-243-597\right)\)
\(=243+597+1996-243-597\)
\(=1996+\left(243-243\right)+\left(597-597\right)\)
=1996
d: \(\left(178-1936\right)-\left[\left(-1936\right)-\left(-178\right)\right]\)
\(=178-1936+1936-178\)
\(=\left(178-178\right)+\left(1936-1936\right)\)
=0+0
=0
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