2.55×1.5+1.5+6.45×1.5=1.5 × (2.55 + 1 + 6.45)=15
2.55×1.5＋1.5×1.5＝1.5×（2.55＋6.45）＝1.5×10＝15
(2.45+6.45)*1.5+1.5
