The information provided showed one trip with an average mileage of 18mpg, and a second trip with an average mileage of 26 mpg.
2. Since we have only this information, the "expected fuel economy" would be half the difference between the two mileages, which is 4 mpg added to 18 mpg for 22 mpg.
The influence of the wind is -8 mpg.
2a. The fuel consumption on the first trip was 1287 miles ÷ 18 mpg = 71.5 gallons. The fuel consumption on the second trip was 1287 miles ÷ 26 mpg = 49.5 gallons.
Driving against the wind required 22 gallons more than driving with the wind.