Question 407950
Let x be the speed of the wind. We note that the 7 hour flight is made with the 
wind pushing the plane. So for the 7 hour flight the distance is 
7*(630+x). For the 8 hour flight we have that the distance is 8*(630-x). So

  7*(630+x)= 8*(630-x)
4410 + 7*x = 5040 - 8*x
      15*x = 630 
         x = 42