Both distances 3966 and 4746 were done in 6 hours, so the speeds are:
speed against wind = 3966/6=661 km/h (difference of airplane and wind)
speed with wind = 4746/6=791 km/h (sum of airplane and wind)
The speed of airplane is greater than that of the wind, so this is a sum and difference problem.
Greater speed (plane) = (sum+difference)/2=(791+661)/2=726 km/h
Lesser speed (wind) = (sum-difference)/2 = (791-661)/2 = 65 km/h
