5.4÷(3.94+0.86)×0.8=5.4÷4.8×0.8=(5.4÷6)×(0.8÷0.8)=0.9×1=0.9
①5.4÷(3.94+0.86)×0.8,=5.4÷4.8×0.8,=1.125×0.8,=0.9;②8×(20-1.25),=8×20-8×1.25,=160-10,=150.