梨树:180÷(3/5-3/7)=1050棵桃树:1050×3/5=630棵苹果树:1050×3/7=450棵
梨树:180÷(3/5-3/7)=180÷(6/35)=1050棵苹果:1050x(3/7)=450棵桃树:450+180=630棵
梨树有:180÷(3/5-3/7)=1050(棵)桃树有:1050×3/5=630(棵)苹果树有:1050×3/7=450(棵)