Question 908517
r*t=d
with the wind
(r+w)*5=3915
(r+w)=3915/5
r+w=783
against the wind
(r-w)*5=3065
(r-w)=3065/5

r-w=613
r+w=783
add
r+r=613+783
2r=1396
r=698
r=698 jet

698-w=613
w=698-613
w=85 wind
check
(698+85)*5=3915
783*5=3915
3915=3915
ok
(r-w)*5=3065
(698-85)*5=3065
613*5=3065
3065=3065
ok