The new tires in George's vehicle are 15.5 inches in diameter. They are guaranteed for 75,000 miles, meaning that the thread will wear less than 0.50 inches in 75,000 miles. When he got his new tires, George had determined that he was getting an average of 34.55 miles per gallon of fuel. He got suspicious of the tires when, after 25,000 miles of driving, his mileage improved to 35.00 miles per gallon; and he was sure of his problem when after another 25,000 miles, his mileage was 35.47 miles per gallon.

Please, use the information given to help George make a case to return his defective tires.

George is already getting pretty good gas mileage.
Have you read this:
https://www.askmehelpdesk.com/other-subjects/announcement-font-color-ff0000-u-b-read-first-expectations-homework-help-board-b-u-font.html

I think George would be hard pressed to make a case that the change in fuel economy could be attributed solely to the diameter of his tires. Air temperature, speed, # of stops, engine condition, weather (rain/snow/wind) and a very long list of other reasons would prevent getting 4 digits of significant digits in your MPG.