42.53*8.9+69.47*8.9-6*17.8＝?
问题描述：
42.53*8.9+69.47*8.9-6*17.8＝?
答
42.53*8.9+69.47*8.9-6*17.8
=（42.53+69.47）×8.9-6×17.8
=112×8.9-6×2×8.9
=（112-6×2）×8.9
=100×8.9
=890
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