a) A=-[-506+732-(-2000)]-(506-1732)
=506-732+(-2000)-506+1732
=(506-506)+(1732-732)+(-2000)
=0+1000+(-2000)
=-1000
b)B=1037+{743-[1031-(+57)]}
=1037+(743-1031+57)
=1037+743-1031+57
=(1037+743)-(1031-57)
=1780-974
=806
c) C=(125.73-125.75):(-25.2)
=[125.(73-75)]:(-25.2)
=]125.(-2)]:(-50)
=(-250):(-50)
=50
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