Question

1又三分之一减去十二分之七加二十分之九减去三十分之十一加上四十二分之十三减去五十六分之十五

没有数字，请你们写下来，求简便方法过程

Answer 1

4/3-7/12+9/20-11/30+13/42-15/56
=1/3(4-7/4)+1/10(9/2-11/3)+1/14(13/3-15/4)
=1/3(4-7/4)+1/10(4+1/2-4+1/3)+1/14(4+1/3-4+1/4)
=1/3*9/4+1/10*5/6+1/14*7/12
=9/12+1/12+1/24
=21/24
=7/8