(+1)+(-21/2)+(-83/37)+(-9.5)
=1-21/2-83/37-19/2
=1-21/2-19/2-83/37
=1-(21/2+19/2)-83/37
=1-20-83/37
=-19-83/37
=-19-2-9/37
=-21-9/37
=-21又9/37
(+1)+(-21/2)+(-83/37)+(-9.5)
=1-21/2-83/37-19/2
=1-21/2-19/2-83/37
=1-(21/2+19/2)-83/37
=1-20-83/37
=-19-83/37
=-19-2-9/37
=-21-9/37
=-21又9/37