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Let u be the speed of the plane at no wind.
Then the effective speed with the wind is (u+60) mph; against the wind (u-60) mph.
The total distance is the same in both directions, therefore
2.4*(u+60) = 2.76*(u-60).
From this equation u = = 860 mph.
So, the airplane speed at no wind is 860 mph.
Hence, the effective speed with the wind is 860+60 = 920 mph
and the distance is 2.4*920 = 2208 miles. ANSWER
Solved.
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Notice that the Internet gives another distance between two cities (about 1000 miles).
My solution HAS NO errors - it is correct.
It means that the input data is not consistent with reality --- or the airplane flies along very curved path.