8/9-5/12= 7/15-3/20-1/20+3/15 =(7/15+3/15)-(3/20+1/20) =10/15-4/20 =
问题描述:
8/9-5/12= 7/15-3/20-1/20+3/15 =(7/15+3/15)-(3/20+1/20) =10/15-4/20 =
7/15-3/20-1/20+3/15 =(7/15+3/15)-(3/20+1/20) =10/15-4/20 = 是7/15-3/20-1/20+3/15 =(7/15+3/15)-(3/20+1/20)
=10/15-4/20
= (简算)
答
8/9-5/12=32/36-15/36=17/36
7/15-3/20-1/20+3/15
=(7/15+3/15)-(3/20+1/20)
=10/15-4/20
=10/15-1/5
=10/15-3/15
=7/15