20*12.5*0.8*0.5 =(20*0.5)*(12.5*0.8)=10*10=100
0.125*0.25*0.5*64 =0.125*0.25*0.5*8*4*2=(0.125*8)*(0.25*4)*(0.5*2)=1
15.7÷0.12+184÷9.6 =1570/12+230/12=(1570+230)/12=1800/12=150
117.8÷2.3-4.88÷0.23 =1178/23-488/23=(1178-488)/23=690/23=30
4.92÷0.25÷4=4.92/(0.25*4)=4.92/1=4.92
36.36÷（1.212×4）=36.36/1.212/4=30/4=7.5
47.85÷6.38×0.638 =47.85/(6.38/0.638)=47.85/0.1=478.5
66.66÷12.5÷0.4÷0.8÷0.3 =(66.66/0.3)/(12.5*0.8*0.4)=222.2/4=55.55
99.9×0.28-0.666×37=3.33*3*2.8-3.33*2*3.7=3.33*(3*2.8-2*3.7)=3.33