（2/1+0.25）除以（2-1.25乘0.6）
=(1/2+1/4)/(2-5/4*3/5)
=3/4/(5/4)
=3/4*4/5
=3/5
1351-103
=1000+300+51-100-3
=1000+300-100+51-3
=1000+200+48
=1200+48
=1248
5.03-2.73-0.2
=5.03-(2.73+0.2)
=5.03-2.93
=5.03-3+0.07
=2.03+0.07
=2.10
4.3乘10.1
=4.3*(10+0.1)
=4.3*10+4.3*0.1
=43+0.43
=43.43