1-2/5+4/7等于多少?1-2/5+4/7=3/5+4/7 =21/35*20/35 =41/35
=1-14/35+20/35=21/35+20/35=41/35
1-2/5+4/7=35/35-14/35+20/35=(35-14+20)/35=41/35=1+6/35