口算．
2﹣0.7= 7.8+2= 5.74+0.26= 0.06+0.5=
4.6+5.4= 7.52﹣2.52= 1﹣0.25= 0.9﹣0.09=
2.8+28= 0.6+0.7= 0.64﹣0.6= 3.5﹣2.8=
口算．
2﹣0.7= 7.8+2= 5.74+0.26= 0.06+0.5=
4.6+5.4= 7.52﹣2.52= 1﹣0.25= 0.9﹣0.09=
2.8+28= 0.6+0.7= 0.64﹣0.6= 3.5﹣2.8=
3×(2x +7) =45
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