Question 1202478
Going to, speed {{{V[1]}}}
Returning, speed {{{V[2]}}}
Total Trip time, {{{T}}}
distance either direction, d
-
{{{system(V[1]=3,V[2]=7,T=10)}}}

<pre>
             SPEEDS         TIME                DISTANCE

GOING        {{{V[1]}}}          {{{d/V[1]}}}                 d

RETURN      {{{V[2]}}}           {{{d/V[2]}}}                 d

Total                          {{{T}}}
</pre>
{{{T=d/V[1]+d/V[2]}}}


{{{T=d(1/V[1]+1/V[2])}}}

multiply both sides by {{{V[1]V[2]}}};

{{{TV[1]V[2]=d(V[2]+V[1])}}}

{{{highlight_green(d=T(V[1]V[2])/(V[2]+V[1]))}}}


To evaluate with your given values
{{{d=(10*3*7)/(7+3)}}}
.
.
{{{d=21}}}