Question 1127952
<pre>
                  speeds        times         distances

first part         r            70/r           70

second part       r-4           30/(r-4)       30

total                           8
</pre>
{{{70/r+30/(r-4)=8}}}


{{{35/r+15/(r-4)=4}}}

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simplifies into {{{2r^2-33r+70=0}}}


discriminant, {{{33^2-4*2*70=529=23^2}}};


{{{r=(33+23)/4}}}  because you will find the MINUS form will not work;


{{{highlight(r=13&3/4)}}}-------for the first part of trip.