设桃树为X棵 苹果树为Y 梨树为Z
1.果园里的桃树比苹果树少50棵
Y - X = 50
2.苹果树棵数的1/3和桃树的40%相等
Y/3 = 0.4*X
3.Z/Y = 2/3
互相带入可得
X = 250
Y = 300
Z = 200