4392+2997=4392+3000-3=7392-3=7389
5364-1999=5364-2000+1=3364+1=3365
25/2.5/4=25/(2.5*4)=25/10=2.5
125/(50/8)=125*8/50=1000/50=20
68*0.99=68*(1-0.01)=68-0.68=67.32
7.2*1.02=7.2*(1+0.02)=7.2+7.2*0.02=7.2+0.144=7.344
3.72-(1.72+1.3)=3.72-1.72-1.3=2-1.3=0.7
7.7*7+7.7+2*7.7=7.7*(7+1+2)=77
8/9-(8/9-9/25)=8/9-8/9+9/25=9/25=36/100=0.36
38.75-15.38+61.25-4.62=(38.75+61.25)-(15.38+4.62)=100-20=80
4.6*8+4又5/8-2又7/11-1又4/11=4.6*8+4.625-(2又7/11+1又4/11)=4.6*8+4.625-4=
8又17/32+5又1/4-6又17/23+0.75=8又17/32+5又1/4-6又17/32+3/4=8
5又3/7*0.5/5又3/7*0.5=1
(5又5/9-0.8+2又4/9)*125=(8-0.8)*125=8*125-0.8*125=1000-100=900
2001*0.64+2001*0.36=2001*(0.64+0.36)=2001*1=2001
64.5*1/11+1/11*34又1/2=(64.5+34.5)*1/11=99/11=9