Question 976204
against the wind: speed jet = speed without wind - speed wind
with the wind speed jet = speed w/o wind + speed wind

time = distance/speed = d/(s-w) = 6h
time return - d/(s + w) = 5h

so 6*(s-w) = 5 (s+w)
s = 11 w

so s-w = 10w = d/6 = 4860/6 = 810 which gives 

w = 81 mph
s= 891 mph