Question

A plane can fly 310 mph in still air. if it can fly 185 miles downwind in the same amount of time it can fly 125 miles upwind, find the velocity of the wind.

Answer 1

Let x be the velocity of the wind, then
(310+x) = plane speed downwind
(310-х) = plane speed upwind 

$\frac{185}{310+x} = \frac{125}{310-x} \\ 185(310-x)=125(310+x) \\ 57350-185x=38750+125x \\ 57350-38750=125x+185x \\ 18600=310x \\ x=60 \ mph$

Answer: 60 mph.