苹果+梨=0.55;梨+桃=0.52式等号两边相减:苹果+梨-梨-桃=0.55-0.5;即苹果-桃=0.05,又:苹果+桃=0.452式等号两边相加:苹果-桃+苹果+桃=0.05+0.45,即苹果+苹果=0.5,2个苹果=0.5,1个苹果=0.5÷2=0.25(千克);苹果+桃=0.45,...