Answer: the speed of the plane is 300 miles per hour
The strength of the tail wind is 400 miles per hour
Explanation:
A tail wind travels in the direction of the airplane. It took the plane 3 hours to travel 2100 miles with a tail wind.
Speed = distance / time
The speed of the airplane while travelling with the tail wind is
2100/3 = 700 miles per hour.
It took the plane 7 hours to make the return trip against the wind. This means that the plane travelled the same distance of 2100 miles back in 7 hours.
The speed of the plane while travelling back would be
2100/7 = 300 miles per hour
The speed of the wind would be
the speed while it was flying with the tail wind - the speed when it was flying against the tail wind . it becomes
700-300 = 400 miles per hour