{5/2(x+y)= 1200, 10/3(x-y)= 1200
x=420,y=60
A: The average speed of the plane is 420km/h and the wind speed is 60km/h..
2. Let the average speed be x km/h on the first day and y km/h on the second day.
{5y-4x=2,4x+5y=98
x= 12,y= 10
Answer: the average speed on the first day is 12km/h, and the average speed on the second day is10 km/h.