Question 1127565
{{{system(r-w=1260/3.5,r+w=1260/3)}}}


-


{{{w+1260/3.5=-w+1260/3}}}

{{{2w=1260/3-1260/3.5}}}

{{{2w=60}}}

{{{highlight(w=30)}}}---------speed of wind


{{{highlight(390=r)}}}--------speed of plane in absence of wind