Question 908822
I'm glad to help you.  I am a Chinese student and I think there's something different between our classes. :) 

let the speed of the helicopter in still air = x
let the wind speed = y
 
then you can get a linear equation of two unknowns.

2·(x-y)=264  [upwind flight distance ]
2·(x+y)=396  [downwind flight distance]

then solve it.

Okay.