8.6×2.7＋0.86×720＋0.86
=0.86×27+0.86×720+0.86×1
=0.86×（27+720+1）
=0.86×748
=643.28
3.4×5.2＋0.34×47＋ 0.34
=0.34×52+0.34×47+0.34
=0.34×（52+47+1）
=0.34×100
=34