5.7*16.2+16.2*4.3-6.2*4.8+6.2*5.2=(5.7*16.2+16.2*4.3)-(6.2*4.8+6.2*5.2)=16.2(5.7+4.3)-6.2(4.8+5.2)=16.2*10+6.2*10=10(16.2-6.2)=10
13.4+12.3+11.2+10.4-11.5-12.6-0.4=(13.4+12.3+11.2+10.4)-(11.5+12.6+0.4)=47.3-24.5=22.8
?????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????