Question 1202341
Follows an often used form.
Here unknown variable, x for unknown time to run.

<pre>
              SPEED          TIME        DISTANCE

RAN TO            r             x          d

WALKED BACK       w            t-x        d

TOTAL                           t        2d
</pre>
{{{rx=w(t-x)}}}

{{{rx=wt-wx}}}

{{{rx+wx=wt}}}

{{{highlight_green(x=(wt)/(r+w))}}}



You are given r=7, w=3, and t=20.
Evaluate x.
Then {{{d=rx}}}.