7.49-[o.56=2.49] 21.43-2.17-7.83=8.57 都用简便计算
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7.49-[o.56=2.49] 21.43-2.17-7.83=8.57 都用简便计算
![7.49-[o.56=2.49] 21.43-2.17-7.83=8.57 都用简便计算](/uploads/image/z/210145-49-5.jpg?t=7.49-%5Bo.56%3D2.49%5D+21.43-2.17-7.83%3D8.57+%E9%83%BD%E7%94%A8%E7%AE%80%E4%BE%BF%E8%AE%A1%E7%AE%97)
7.49-(0.56+2.49)=7.49-0.56-2.49=7.49-2.49-0.56=5-0.56=4.44
21.43-2.17-7.83+8.57=21.43+8.57-2.17-7.83=(21.43+8.57)-(2.17+7.83)=30-10=20
21.43-2.17-7.83+8.57=21.43+8.57-2.17-7.83=(21.43+8.57)-(2.17+7.83)=30-10=20