Winter vacation life's math problem in the fifth grade of Shanghai Education Press.

(1) Solution: If the ballpoint pen costs X yuan, the pen costs 3x yuan.

3x+x= 18，x=4.5，3x= 13.5

Answer: The price of a ballpoint pen is 4.5 yuan, while the price of a pen is 13.5 yuan.

(2) Solution: If there are x pear trees, there are 2x-40 apple trees.

x+2x-40=500，x= 180，2x-40=320

A: There are 180 pear trees and 320 apple trees.

(3) Solution: Let each bag of rice have X kilograms.

700x-300x=4000，x= 10

300 times = 3000,700 times =7000

A: I sold 7,000 Jin of rice in the morning and 3,000 Jin of rice in the afternoon.

(4) Solution: If the banana is X yuan per kilogram, then the apple is x+ 1.2 yuan per kilogram.

3x+5(x+ 1.2)=4 1.2

x=4.4

4.4 yuan per kilogram of bananas.