Question 668525
d=rt OR    t=d/r
t=320/(120-w)
t=640/(120+w)
320/(120-w)=640/(120+w)
640(120-w)=320(120+w)
76,800-640w=38,400+320
-640w-320w=38,400-76,800
-980w=-38,400
w=-38,400/-960
the wind speed is 40 mph