①1.25×2.5×（0.4×0.8)=(1.25×0.8)×(2.5×0.4)=1×1=1②(0.8+1.2)/0.08=2/0.08=200/8=25③11/[(0.4+0.04)×0.5]=11/[0.4×0.5+0.04×0.5]=11/[0.2+0.02]=11/0.22=1100/22=100/2=50哪里不清欢迎追问，满意谢谢5颗星采纳！
