Question 1200756
<pre>
               SPEED         TIME        DISTANCE
AGAINST        r-w            7           1015
WITHWND        r+w            4            820
</pre>
{{{system((r-w)(7)=1015,(r+w)(4)=820)}}}


{{{system(r-w=1015/7,r+w=820/4)}}}


{{{ADD}}}{{{corresponding}}}{{{members}}}

{{{2r=1015/7+820/4}}}

{{{r=(1/2)(1015/7+820/4)}}}-----plain, still air
{{{AND}}}
{{{w=(1/2)(820/4-1015/7)}}}----wind