0.7777X0.7十0.1111X2.1
=0.1111x [(7x0.7)+2.1]
= 0.1111x (4.9+2.1)
=0.1111x7
=0.7777
0.7777×0.7+0.1111×2.1
=0.1111×7×0.7+0.1111×3×0.7
=0.1111×[(7+3)×0.7]
=0.1111×7
=0.7777
0.7777×0.7+0.1111×2.1
＝0.1111×（7×0.7）+0.1111×2.1
＝0.1111×（4.9+2.1）
＝0.1111×7
＝0.7777
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