4又3⼀5-（1又2⼀9+2.6） 1⼀2+1⼀6+1⼀12+1⼀20+1⼀30

1/2乘进后用加减法合并分母为5、20、30、10的项和分母为9、6、12的项再将得数相加

4又3/5-（1又2/9+2.6） 1/2+1/6+1/12+1/20+1/30
=23/5-(11/9+26/10) =1/2+(1/2-1/3) +(1/3-1/4) +(1/4-1/5)+(1/5-1/6)
=23/5-(110/90+234/90) =1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6
=414/90-344/90 =1-1/6
=7/9 =5/6

能否看懂？

4又3/5=4.6
4又3/5-（1又2/9+2.6）
=4.6-2.6-1又2/9
=1又9/9-1又2/9
=7/9
1/2+1/6+1/12+1/20+1/30
=6/12+2/12+1/12+3/60+2/60
=9/12+1/12
=5/6