21-49.9+10.2-2-3.5+19=?
1个回答

=(21-2+19)-(50-0.1)+(10+0.2)-3.5

=38-50+0.1+10+0.2-(3+0.5)

=(38-50+10-3)+(0.1+0.2-0.5)

=-5-0.2

=-5-1/5

=-(5+1/5)

=负5又5分之1

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