Answer:
about 323.9 mph
Explanation:
You want the speed of a plane that travels 750 miles in 2 hours with the wind and in 2.75 hours against the wind.
Speed
The relation between time, distance, and speed is ...
speed = distance/time
If p represents the speed of the plane, and w represents the speed of the wind, then we have ...
p +w = 750/2 . . . . . . miles/hour with the wind
p -w = 750/2.75 . . . . speed against the wind
Solution
Adding these two equations gives ...
2p = 750(1/2 +1/2.75) = 750(4.75/5.50)
Dividing by 2, we have ...
p = 375(19/22) ≈ 323.9 . . . . . miles per hour
The plane was flying about 323.9 miles per hour.
__
Additional comment
The wind speed was about 51.1 miles per hour.